### Answer Based on the available documentation, Elastic SIP Trunking is the recommended method to integrate your Twilio number with Retell AI [(1) ]() [(2) ]() . The documentation indicates that "Connect via SIP Trunking" is the correct integration method when adding Twilio numbers to Retell [(2) ]() . There is mention of an alternative approach called "Method 2: Dial to SIP Endpoint" for custom telephony [(3) ]() , but this method has known issues including a ringing sound that callers hear after answering, which occurs due to call redirection . This method is typically used when users cannot set up SIP trunks . To connect your Twilio number via SIP Trunking [(1) ]() : 1. Create Elastic SIP Trunking in Twilio - Set up termination (outbound) and origination (inbound) with Retell's SIP server address:

sip:sip.retellai.com

2. Move your Twilio number to the SIP trunk 3. Import the number to Retell - Use the dashboard or the Import Number API, providing your termination SIP URI and authentication credentials [(1) ]() [(4) ]() Once imported, your number will function like a Retell-purchased number for both inbound and outbound calls [(1) ]() .

​ To learn more, see the sources I considered: [[1] Twilio](https://docs.retellai.com/deploy/twilio) [[2] Enable the Twilio provider module](https://community.retellai.com/t/enable-the-twilio-provider-module/178) [[3] Custom Telephony](https://discord.com/channels/1186424376300679209/1290731680969261059) [[4] Import Phone Number](https://docs.retellai.com/api-references/import-phone-number) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.