In this guide
What are the best Synthflow alternatives for agencies after rebilling was removed?
For agencies replacing Synthflow's in-product customer billing, evaluate Assistable, Autocalls and Trillet for an integrated agency platform, VoiceAIWrapper for a branded layer across supported voice providers, or Retell when you want to own more of the application and billing stack. Keeping Synthflow with external billing is also valid. Assistable is a strong fit when you want eligible-plan Stripe usage rebilling, white-label client accounts and HighLevel-connected voice and conversational AI together.
Key points
- Compare the whole agency workflow
- Verify billing before migrating
- Use current provider terms
Compare the operating models.
This is an Assistable-authored comparison based on the linked vendor documentation, not an independent ranking or a benchmark of voice quality. We compare operating fit rather than assigning unsupported scores.
| Option | Best fit to evaluate | Billing and delivery boundary |
|---|---|---|
| Assistable | Agencies delivering branded, CRM-connected voice and conversational AI with client usage pricing. | Stripe usage wallets and white labeling on eligible agency plans. Review monthly retainers and legacy subscriptions separately. |
| Autocalls | Agencies prioritizing a branded resale portal with their own monthly client plans. | Publishes Stripe Connect, included-minute plans and overage on Agency White Label. Confirm current package, number and destination-rate terms. |
| Trillet | Agencies seeking a white-label platform with published Studio and Agency packages. | Published Stripe invoicing; custom minute markup and custom domain on Agency. Telephony and some usage costs are separate. |
| VoiceAIWrapper | Agencies that want a branded portal over Retell, Vapi or ElevenLabs. | Published client billing and rebilling. Provider connections depend on plan or add-on; underlying provider usage is separate. |
| Retell | Teams that want a voice/chat platform and can assemble the surrounding agency experience. | Published APIs, webhooks and usage pricing. Confirm or build the client portal, subscriptions and billing integration your offer requires. |
| Keep Synthflow | Agencies with working agents that prefer to replace only the commercial workflow. | Keep subaccounts and branding; collect, reconcile and report customer charges in an external billing system. |
Where Assistable fits.
Assistable brings the client account, agent workflow and usage rebilling into an agency platform. Configure your brand, connect Stripe, set supported client prices and deliver agents that can answer, qualify, book, follow up and hand conversations to a person.
- Start with the dashboard and connected tools; use APIs where the client needs custom behavior.
- Connect HighLevel subaccounts and calendar tools, then validate the correct contacts, fields and calendars.
- Reuse snapshots for new-account defaults without treating them as updates to existing live accounts.
- Use Startup, Growth or Agency for usage rebilling and white labeling. The Solo plan excludes those features.
When another option makes sense.
If your priority is keeping an existing provider, a wrapper can be more relevant than replacing the full agent stack. If you have developers and a custom application, a platform API may fit better than an integrated agency portal.
Autocalls: compare the client plan designer
Its published Agency White Label package is $419 per month with 3,500 included minutes, $0.09 per extra minute and unlimited client subaccounts. It advertises your own Stripe connection and client plans with included minutes and overage prices. Confirm the current package and destination-rate terms against the service you sell.
Trillet: compare the agency package
Its current Studio plan is $99 per month with three workspaces. Agency is $299 with unlimited workspaces, a custom domain and custom minute markup. Confirm included minutes, telephony, transferred-call and workflow charges against your usage.
VoiceAIWrapper: compare the provider layer
Its published plans include Stripe and external billing. Review the number of client portals, provider connection access and the separate bill from Retell, Vapi or ElevenLabs before comparing total cost.
Retell: compare what you will build
Its published offer includes voice and chat agents, APIs, webhooks, templates and testing. Ask for a demonstration of the exact client billing and portal requirements, or include a separate agency layer in the budget.
Synthflow plus external billing: preserve the agent
If the agent and integrations already satisfy your clients, use the retained API and usage controls with an external billing process. Assign an owner for metering, renewals, exceptions and customer reporting.
Ask every provider to show the same six things.
Use one representative client and the same acceptance criteria. A feature label is less useful than seeing the client rate, usage record and business action agree.
| Check | What to verify |
|---|---|
| Client pricing | Can you set the rate or package you sell, and which plan enables it? |
| Collection | What happens when a balance runs low or a payment fails? Who funds platform usage? |
| Client experience | Which screens, domain, billing details and support links will the client see? |
| CRM action | Does a real booking, contact update or transfer land in the right account? |
| Deployment repeatability | What can be templated, and what needs new authorization or per-client configuration? |
| Exit and rollback | Can you retain records, control number routing and stop the new workflow if an acceptance check fails? |
Common questions
Which Synthflow alternative supports agency rebilling?
Assistable documents Stripe usage rebilling on eligible agency plans. Autocalls publishes Stripe Connect and client plans on Agency White Label. Trillet publishes Stripe invoicing and Agency-plan minute markup. VoiceAIWrapper publishes client billing and rebilling over supported providers. Verify monthly packages, prepaid balances, provider charges and client access before choosing.
Is every voice AI platform suitable for reselling?
No. Agent creation and API access do not establish a branded client portal or customer billing workflow. Evaluate account separation, client pricing, collection, reporting, permissions and support alongside agent quality.
Is keeping Synthflow an option?
Yes. The official removal notice retains subaccounts, branding, custom domains, products and usage limits. Agencies can keep the platform and manage customer billing through their own Stripe or another system.
Which alternative works with GoHighLevel?
Assistable has documented HighLevel authorization, CRM actions and calendar tools. Trillet and VoiceAIWrapper also publish HighLevel integrations, and Synthflow retains its integration. Compare the actual trigger, booking, contact-sync and billing behavior your agency uses.
Should my agency choose an integrated platform or a voice API?
An integrated agency platform is a useful starting point when you need client accounts, branding and usage billing alongside agent delivery. A voice API can fit when your team wants to build and maintain its own application, commercial workflows and customer experience. Include that operating work in the comparison.
Sources & review notes
Reviewed October 17, 2026. Published by Assistable.ai, a provider included in these comparisons. Official documentation establishes the stated features and changes; it does not establish migration results. Confirm your account-specific terms with the relevant provider.
- Synthflow: reselling migration
Removal date, affected features, retained controls and external billing options.
- Assistable: usage rebilling
Stripe setup, client prices, subaccount activation and defaults.
- Assistable: client wallet
Prepaid balance, payment method and automatic top-up configuration.
- Assistable: agency wallet
The agency funds a separate platform-usage ledger.
- Assistable: agency plans
Current plan eligibility and account allowances. Usage is additional.
- Assistable: HighLevel setup
- Assistable: snapshots
- Autocalls: agency pricing and client plan features
Vendor-published package and capabilities, not an independent product test.
- Autocalls: published agency billing model
Used for its own Stripe Connect description, not its competitor characterizations or migration-time claims.
- Trillet: white-label plans and billing features
- VoiceAIWrapper: agency plans and provider costs
- Retell: current platform offer
- Synthflow: retained HighLevel integration