In this guide
Can I keep my phone numbers when moving from Synthflow to Assistable?
Potentially. The route depends on who controls the number and its carrier. Synthflow says numbers connected through your own Twilio account remain in Twilio, while parent-owned numbers assigned to subaccounts remain owned by the parent workspace. Assistable documents importing Twilio numbers through Elastic SIP Trunking. Numbers purchased through Synthflow need an owner and provider review before any port or routing promise. Keep service active until the agreed replacement has been tested.
Key points
- Confirm ownership first
- Routing is different from porting
- Test voice and messaging separately
Find the owner, then choose the route.
A number visible in a client dashboard is not necessarily owned by that client account. Match each number to the account that bought or imported it, the carrier that hosts it and the person authorized to change it.
| Your current setup | What the source establishes | Your next step |
|---|---|---|
| Your own Twilio account | Synthflow's Twilio documentation says the numbers remain in Twilio. | Confirm carrier access and scope a supported routing change. Assistable documents a Twilio Elastic SIP connection. |
| Your own SIP carrier or PBX | Synthflow connects to the existing carrier or phone system. | Have the authorized phone-system owner review a new route and its supported features. |
| Number purchased through Synthflow | The workspace manages its assignment and subscription. | Ask the controlling account and provider for the available port or routing process before scheduling a move. |
| Parent number assigned to a subaccount | Assigning it does not change ownership. The parent retains control. | Include the parent account owner in the migration; client login access alone is not enough. |
| Number purchased by the subaccount itself | Synthflow identifies it as that subaccount's number. | Confirm that account's owner, subscription and provider process. |
A routing change is not a carrier port.
Changing where calls go can preserve the carrier account. Porting changes the carrier serving the number. Forwarding is another possible routing approach, but it does not automatically move messaging or every calling feature.
Assistable's Twilio guide describes Elastic SIP Trunking. Treat that as a supported configuration path to evaluate, not proof that a specific live trunk can be switched without preparation. Obtain the current account-specific settings and test them before changing production routing.
| Option | What changes | What to confirm |
|---|---|---|
| SIP or carrier routing | The destination handling calls while the carrier retains the number. | Authorization, inbound and outbound routing, credentials, caller ID, transfers and supported configuration. |
| Call forwarding | The current service sends selected calls to another destination. | Carrier support, forwarding fees, caller ID, busy/no-answer behavior and the separate SMS route. |
| Carrier port | The carrier responsible for the number. | Portability, owner authorization, account information, timing, messaging and a confirmed completion process. |
Record the details that make recovery possible.
For each client number, keep an operational inventory in your approved secure system. Do not put passwords, authorization tokens or SIP credentials into a shared migration spreadsheet.
- The number in international format, client name, account owner and carrier.
- Current inbound destination, outbound identity, voicemail, transfer path and operating hours.
- Which system sends and receives SMS or WhatsApp, with its registration and consent requirements.
- The authorized routing owner and where current settings are securely recorded.
- Cutover window, test contacts, rollback trigger and support coverage.
- Any account, number subscription or integration that must remain active until verification is complete.
Check the whole number, not just the first inbound call.
Voice routing and messaging can depend on different configurations. Synthflow's Twilio documentation separately discusses voice routing, messaging and A2P requirements. A successful voice call is not evidence that SMS delivery or registration moved with it.
| Check | Pass condition before completion |
|---|---|
| Inbound voice | A call from an outside phone reaches the correct client agent with usable two-way audio. |
| Outbound voice | An authorized test call connects with the intended caller identity. |
| Human handoff | The intended destination receives the transfer, and no-answer or voicemail behavior matches the plan. |
| After-hours behavior | The correct schedule, fallback or voicemail path works when the team is unavailable. |
| SMS and other messaging | The intended provider, sender, registration and opt-out handling are separately verified for any channel in scope. |
| Recovery | The routing owner can restore the approved prior destination if a required check fails. |
Keep the old service until the new route is proven.
Bring the number inventory and current carrier setup to the migration evaluation. We can scope the supported path alongside the agent, CRM workflow and billing transition. Timing depends on the actual number and routing requirements.
Agree on the change
Confirm owner authorization, supported configuration, success checks and the exact rollback trigger.
Move the selected route
Change one agreed client route, then verify inbound, outbound and any required messaging before expanding.
Observe and reconcile
Review call outcomes, transfers, CRM actions and carrier charges during the agreed observation period.
Retire only unused dependencies
Cancel or remove an old number subscription or integration only after checking ownership, portability and continuing service dependencies.
Common questions
Will I lose my number if I leave Synthflow?
Do not assume either loss or guaranteed portability. Confirm who owns the number, which carrier hosts it and which migration path is available. Keep the current service active while that is resolved.
Do I need to port a number that is already in my Twilio account?
Not necessarily. Synthflow says your own Twilio numbers remain in Twilio. Assistable documents a Twilio Elastic SIP connection, so a supported routing change may be an option. Review the current account, trunk and messaging configuration before deciding.
Can a client move a number assigned by the agency?
Synthflow says assigning a parent-owned number to a subaccount does not transfer ownership. The parent remains the controlling account. Include that owner and the carrier in any routing or porting request.
Does switching voice routing also move SMS?
Voice routing and messaging need separate checks. Confirm the messaging provider, sender registration, consent and opt-out handling. Forwarding a voice call does not move its SMS delivery path.
Should I delete my Synthflow number before moving it?
No. Do not delete or cancel a number you still need while ownership and the replacement route are unresolved. Synthflow says deleting a purchased number also cancels its number subscription.
How long does moving client numbers take?
Timing depends on your carrier, ownership and integrations. Validate one route and retain a rollback plan before moving traffic. Agree on the cutover window only after the number owner and supported path are confirmed.
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: consolidated phone-number guide
- Synthflow: parent and client number ownership
- Synthflow: telephony paths
- Synthflow: Twilio routing and messaging
- Assistable: Twilio import
Use current account-specific routing and authentication settings; this guide is not a live configuration audit.
- Assistable: human call transfers