# Keep client billing connected to the service you sell.

Set the client price. Understand the real cost. Make the path from usage to payment something your agency can operate every month.

Published: 2026-10-17

Reviewed: 2026-10-17

## How can agencies replace Synthflow's removed Stripe rebilling?

You can keep Synthflow and run customer subscriptions, usage collection and invoices in an external billing system, or move to an agency platform with supported usage rebilling. Assistable connects Stripe to eligible agency accounts, lets you configure client usage prices and supports prepaid client wallets. The agency separately funds its platform wallet. This is a usage-billing model, so review monthly retainers and existing Synthflow subscriptions separately.

- Client price and platform cost are different
- Two balances to operate
- Model the complete cost

## Know what your agency keeps.

The page includes an editable billing worksheet. It models usage revenue and costs, not wallet deposits or a customer result. Calculations run in the browser without form submission.

Illustrative inputs: 10000 monthly billable minutes, $0.25/minute charged to clients, $0.105/minute variable cost, $225/month platform subscription, $300/month support and other costs, 2.9% payment processing and $5 monthly fixed payment fees.

Modeled usage revenue: $2500.00. Variable usage cost: $1050.00. Payment processing: $77.50. Estimated contribution after the costs entered: $847.50.

Modeled break-even client rate: $0.1627/minute at the entered volume and costs. This divides usage cost, subscription, delivery costs and fixed payment fees by billable minutes after allowing for the percentage payment fee. It is not a recommended selling price. No finite break-even rate is shown when minutes are zero or the payment fee is 100%.

The $0.105/min example combines $0.050 orchestration, $0.020 Standard TTS, $0.020 Kimi K2.6 and $0.015 Assistable telephony, reviewed October 17, 2026. Actual plan or proposal terms govern. Add other usage, carrier fees, phone rental and per-call adjustments to the inputs.

The $225 subscription is the published Startup agency offer. Client price, delivery costs and payment fees are assumptions, not a Stripe quote. Retainers, taxes, refunds, bad debt and unentered costs are excluded. Usage markup is spread divided by usage cost; usage margin is spread divided by revenue. Neither is net profit.

Download the current scenario as a CSV with its inputs, modeled results, formula, assumptions and sources. The scenario is calculated and exported locally in your browser; downloading does not submit or store the values with Assistable.

[Open the editable agency billing worksheet](https://www.assistable.ai/resources/synthflow/rebilling#billing-worksheet)

## Keep the agent. Or bring billing into your agency platform.

The right choice depends on how much commercial infrastructure you want to maintain. Keeping Synthflow preserves a working deployment, but its removed customer billing does not return just because you have a Stripe account.

| Responsibility | Synthflow with external billing | Assistable usage rebilling |
| --- | --- | --- |
| Client price | Maintain prices, subscriptions or invoices in your billing system. | Configure supported client usage rates in Assistable after connecting Stripe. |
| Usage | Collect API counters, post-call durations or call-history totals and reconcile the billing period. | Platform usage is charged against the client wallet at configured rates when rebilling applies. |
| Payment | Own invoice collection, payment failures and any prepaid-credit logic. | Clients fund their wallet through the connected Stripe setup and can configure auto top-ups. |
| Agency cost | Pay Synthflow under your agreement and reconcile that bill against client revenue. | Maintain a separate agency wallet for platform costs. Client funds do not automatically refill it. |
| Recurring packages | Build monthly retainers, included usage and trials in the billing system you choose. | Review recurring retainers or bundled packages separately from documented usage-wallet rebilling. |
| Client reporting | Replace the removed subaccount billing and usage pages with your own reporting. | Review the client wallet and billing experience in the pilot with the intended permissions. |

## Know which balance pays for what.

A client balance and an agency balance serve different purposes. The client funds the service at your configured prices. Your agency pays Assistable for the underlying platform usage. Keeping those two flows visible prevents a healthy client balance from hiding an underfunded agency account.

1. **Connect your agency's Stripe account** Authorize Stripe in Assistable and confirm the correct business account and payment configuration.

2. **Set the client's usage prices** Choose supported fixed prices or markups for the usage categories you sell. Confirm category-specific rules in the billing guide.

3. **Enable the client account** Apply rebilling to the intended subaccount, confirm membership/access and review its wallet setup.

4. **Fund and monitor both balances** The client funds its prepaid wallet and configures any automatic top-up. Your agency separately maintains its platform wallet and monitors exceptions.

- [Stripe connection guide](https://docs.assistable.ai/platform/stripe-integration)
- [Client wallet guide](https://docs.assistable.ai/platform/subaccount-wallet)
- [Agency wallet guide](https://docs.assistable.ai/platform/agency-wallet)
- [Usage pricing rules](https://docs.assistable.ai/v3/billing-guide)

## Price the whole service, not one line on the rate sheet.

An advertised voice rate may cover only part of a conversation. Compare plan fees and usage at the same scope before deciding what to charge clients or what a move could save.

- Use your actual Synthflow agreement for the current-cost baseline. The published enterprise minimum is not every existing customer's bill.
- Assistable's agency subscription does not make all voice minutes, models, carriers or optional features free.
- Client wallet deposits are not automatically earned revenue. Keep prepaid balances, consumed usage and recognized service revenue distinct in your accounting.

| Cost | What to include |
| --- | --- |
| Platform plan | Your agency subscription and any account, capacity or feature allowances. |
| AI conversation | Orchestration, selected speech and language models, and enabled add-ons. |
| Telephony | Carrier usage, transferred-call behavior, number rental and applicable messaging costs. |
| Payments | Payment processing, refunds, failed collections and any billing-system charges. |
| Delivery | Setup, support, monitoring and the work required to operate the client account. |

- [Assistable's current usage rate sheet](https://www.assistable.ai/pricing)
- [Assistable's agency plans](https://go.assistable.ai/pricing)
- [Synthflow's existing-account terms](https://docs.synthflow.ai/billing)

## If you stay on Synthflow, give billing an owner.

Synthflow documents three ways to measure client usage: the subaccount minutes_used counter, call durations from post-call webhooks, or totals from call history. Choose a reliable source, define each client's billing window and reconcile it before issuing charges.

- Keep a mapping between client, Synthflow subaccount and billing customer.
- Define the renewal timestamp, time zone, usage allowance and overage price for each agreement.
- Make ingestion and invoice generation safe to retry so the same usage does not create duplicate charges.
- Reconcile usage before resetting a counter. A reset is not an invoice or proof of payment.
- Decide what a failed payment or usage limit does to the service, and communicate that policy to the client.

- [Synthflow's external metering guidance](https://docs.synthflow.ai/reselling-migration-guide)
- [Synthflow's Auto-overage behavior](https://docs.synthflow.ai/limits-and-capabilities)
- [Stripe's usage billing documentation](https://docs.stripe.com/billing/subscriptions/usage-based)

## Plan for the payment that does not go through.

Automatic top-ups still depend on a valid payment method and successful collection. Give someone responsibility for the exception, not just the setup. Confirm how the approved customer policy matches the account's actual behavior.

| Situation | What to check | Operating decision |
| --- | --- | --- |
| Client cannot see Billing | Membership and account access. Assistable's client-wallet guide requires a member invitation. | Invite the intended billing owner and verify access from their view. |
| Client payment fails | Payment status, remaining balance and top-up configuration. | Assign the notification, recovery and customer communication process. Do not assume a failed payment is recovered automatically. |
| Client wallet is empty | The client-wallet guide documents a pause in AI service until funding is restored. | Agree on the recovery and customer support path before launch. |
| Agency wallet is underfunded | The agency-wallet guide warns that a negative balance blocks voice calling across subaccounts. | Maintain agency funding separately; client balances do not remove that responsibility. |
| Old and new billing overlap | Both billing systems, invoice periods, credits and active subscriptions. | Confirm one intended collection path for each charge and reconcile before expanding. |

- [Documented client-wallet behavior](https://docs.assistable.ai/platform/subaccount-wallet)
- [Documented agency-wallet behavior](https://docs.assistable.ai/platform/agency-wallet)

## Move the billing relationship deliberately.

Your Stripe customers, active subscriptions, stored payment permissions, credits and client contracts are not automatically migrated by creating an Assistable account. Map the commercial arrangement first and approve the next charge with the correct billing owner.

1. **Reconcile the old period** Record what was billed, paid, used, credited and still owed. Preserve the evidence needed for customer questions.

2. **Configure the new relationship** Set the client rate, wallet policy and any separate retainer. Review customer notices and payment authorization requirements.

3. **Test the billing path** With authorization, validate the intended payment and usage flow, correct client ledger and separate agency charge. Check failure behavior as well as success.

4. **Stop duplicate collection** Agree on the old subscription end and new start. Verify the first reconciled period before expanding to more clients.

- [Full migration and acceptance checklist](https://www.assistable.ai/resources/synthflow/migration)

## Plan the billing handoff.

22 acceptance checks covering access, billing, the pilot and cutover. Assign an owner, record evidence and confirm each pass condition before moving a client. Open the CSV in your spreadsheet tool. No email required.

- **Account and access (Inventory):** Authorized owner confirms the client account, users, source access and destination account.
- **Client agreement (Inventory):** Retainer, usage rates, included services, renewal date, cancellation terms and required notice are documented.
- **Billing identity (Billing):** Source subaccount, billing customer and destination client ledger are mapped to the same client.
- **Old billing period (Billing):** Billing owner records the old period's start/end and time zone, consumed usage, invoices, payments and credits.
- **Balance reconciliation (Billing):** Prepaid credits, unpaid invoices and refunds have an agreed treatment; no automatic balance transfer is assumed.
- **New commercial approval (Billing):** Client notice, payment authorization, new rate, billing start and any separate retainer are approved by the billing owner.
- **Stripe account (Billing):** The intended agency Stripe account is connected; its account owner confirms the collection setup.
- **Usage prices and gates (Billing):** The master rebilling setting, intended categories and supported prices match the approved client offer.
- **Client membership and wallet (Billing):** The invited client can access the intended billing portal and configure an authorized payment method, funding and refill policy.
- **Agency funding (Billing):** The separate agency wallet is funded; its refill policy and balance-review owner are established.
- **Payment failure policy (Billing):** The owner confirms what happens to the client service when payment fails or funds run low, and how the client is notified.
- **Agent behavior (Pilot):** The representative agent follows approved knowledge, qualification rules and out-of-scope handling in authorized tests.
- **Calendar action (Pilot):** A permitted test appointment appears in the intended calendar with the correct contact and time zone.
- **CRM write-back (Pilot):** Expected fields, notes and follow-up actions appear once in the correct client account.
- **Human transfer (Pilot):** Successful transfer, no-answer and unavailable-team paths reach the intended destination or configured fallback.
- **Account permissions (Pilot):** The client sees only the intended account, features, branding and billing access.
- **Billing evidence (Pilot):** Authorized test usage, client debit and separate agency cost reconcile to the approved rates; payment collection is checked separately.
- **Number and routing control (Cutover):** The authorized number owner approves the forwarding, SIP or porting path; existing service remains active until routing works.
- **No duplicate activity (Cutover):** Old and new calling triggers and billing collection rules cannot act on the same traffic or billing period unintentionally.
- **Sign-off and rollback (Cutover):** The client/service owner approves the window, pass criteria, rollback trigger and named person able to restore the previous route.
- **First-period review (Review):** Actual calls, appointments, CRM writes, transfers, usage, collections and both balances are reviewed before more clients move.
- **Retire previous services (Review):** Required records are retained and dependencies/contract terms checked before ending old access, subscriptions or number service.

[Download migration checklist](https://www.assistable.ai/resources/synthflow/migration/checklist.csv)

## Common questions

### Can I reconnect Stripe to Synthflow for rebilling?

Synthflow's current documentation says the in-product reselling integration was removed on September 15, 2026 and new Stripe connections are no longer supported. You can use your own Stripe account externally to bill customers.

### Does Assistable automatically refill the agency wallet from client payments?

No. The documented client and agency wallets are separate. Client payments fund the client balance, while your agency must maintain its own platform-usage balance.

### Can I set my own client prices in Assistable?

Yes, on eligible agency plans with rebilling configured. Supported usage categories have fixed-price or percentage-markup rules. Review the current billing guide for each category before setting an offer.

### Does usage rebilling replace my monthly client retainer?

Not automatically. Assistable's documented native model is prepaid usage rebilling. Review retainers, bundled minutes, trial credits and legacy subscriptions as separate commercial requirements.

### Is Synthflow Auto-overage the same as collecting customer payments?

No. Auto-overage keeps the subaccount calling beyond its allocation, but Synthflow charges the agency. The agency must track and bill that usage to its client separately.

### Can I calculate savings from advertised per-minute rates?

Only if the rates cover the same components. Include models, speech, telephony, optional features, plan fees, numbers and delivery costs. Use current agreements and actual bills for the comparison.

### What if my client cannot see their wallet or billing settings?

Assistable's client-wallet documentation requires the client to be invited as a member of the intended account. Verify the invitation, membership and account context before changing billing configuration.

### Do automatic top-ups guarantee uninterrupted service?

No. They depend on payment configuration and successful collection. Monitor the client and agency wallets separately, agree on an exception process and verify the documented behavior for an empty balance before rollout.

## Sources and review notes

Published by Assistable.ai. Confirm account-specific features, pricing and migration scope with each provider.

- [Synthflow: reselling migration](https://docs.synthflow.ai/reselling-migration-guide): Removal date, affected features, retained controls and external billing options.
- [Assistable: usage rebilling](https://docs.assistable.ai/platform/rebilling): Stripe setup, client prices, subaccount activation and defaults.
- [Assistable: client wallet](https://docs.assistable.ai/platform/subaccount-wallet): Prepaid balance, payment method and automatic top-up configuration.
- [Assistable: agency wallet](https://docs.assistable.ai/platform/agency-wallet): The agency funds a separate platform-usage ledger.
- [Assistable: agency plans](https://go.assistable.ai/pricing): Current plan eligibility and account allowances. Usage is additional.
- [Assistable: Stripe integration](https://docs.assistable.ai/platform/stripe-integration)
- [Assistable: usage billing rules](https://docs.assistable.ai/v3/billing-guide)
- [Synthflow: limits and Auto-overage](https://docs.synthflow.ai/limits-and-capabilities)
- [Synthflow: billing and existing agreements](https://docs.synthflow.ai/billing)
- [Stripe: usage-based billing](https://docs.stripe.com/billing/subscriptions/usage-based)

## Related resources

- [A Synthflow alternative built for your agency.](https://www.assistable.ai/compare/synthflow)
- [Move your agency from Synthflow.](https://www.assistable.ai/resources/synthflow/migration)
- [Synthflow alternatives for agencies.](https://www.assistable.ai/resources/synthflow/alternatives)
- [Compare your HighLevel voice AI costs.](https://www.assistable.ai/resources/gohighlevel/voice-ai-pricing)

[Talk to sales](https://www.assistable.ai/contact?booking_source=%2Fresources%2Fsynthflow%2Frebilling)

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Source: https://www.assistable.ai/resources/synthflow/rebilling