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Rubén Ros
03/11/2026, 11:02 AM@AI Evy Hey! I'm having an issue with the Transfer Call node. My number is connected via SIP Trunk (Spanish Twilio number) since Retell doesn't sell Spanish numbers directly.
When the transfer triggers I get this error:
tool_call_id: transfer_call_62e072
{"status":"Transfer call cannot be completed, probably don't have the permission to perform the transfer.. Please inform the customer that the transfer did not go through and offer to try again or assist them directly."}
I think the problem is that in my account the only option to add a phone number is via SIP Trunk — I don't see the native Twilio integration (Account SID + Auth Token) anywhere.
Is there any way to enable native Twilio integration for my account so transfers work? Thanks!
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AI Evy
03/11/2026, 11:03 AMThanks for tagging me @Rubén Ros. I'll look through relevant sources and get back to you shortly.
AI Evy
03/11/2026, 11:03 AM### Answer
Based on the available documentation, "Connect via SIP Trunking" is the recommended method to integrate your Twilio number with Retell AI [(1) ]() . The documentation doesn't mention a separate "Telephony Provider → Twilio" option in the dashboard .
Regarding your transfer issue, when using SIP trunking with cold transfers, there are known limitations. The documentation indicates that you may need to consider alternative approaches [(2) ]() :
1. **Use Warm Transfer**: This provides more control over the transfer process
2. **Custom SIP Headers**: You can add custom SIP headers to transfers, though these may not be honored by Twilio for cold transfers
3. **Direct API Integration**: Work with your transfer destination to accept call context through other means (webhooks, custom headers, etc.)
The "Connect via SIP Trunking" option you're seeing is the correct integration method for bringing your own Twilio number [(1) ]() . Once imported, your number will appear in your dashboard and function like a Retell-purchased number .
If you need additional assistance with the setup, you can:
- Visit [Contact Sales]()
- Ask questions on [Discord]()
- Visit
AI Evy
03/11/2026, 11:03 AM
To learn more, see the sources I considered:
[[1] Enable the Twilio provider module](https://community.retellai.com/t/enable-the-twilio-provider-module/178)
[[2] Help on Twilio DID questions](https://community.retellai.com/t/help-on-twilio-did-questions/24)
AI Evy
03/11/2026, 11:03 AMFeel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.