### Answer To set up Twilio with your Retell AI voice agent, follow these steps: ## 1. Set Up Elastic SIP Trunking in Twilio Create a SIP trunk in your Twilio dashboard and configure it with the following settings [(1) ]() : Configure Origination (Inbound Calls) : - Set Retell AI's SIP server address as the origination SIP URI:

sip:sip.retellai.com

[(2) ]() - For toll-free numbers, use:

sip:sip.retellai.com;transport=tcp

Configure Termination (Outbound Calls) : - Specify the termination SIP URI provided by Twilio [(1) ]() - Choose between IP whitelisting or credential-based authentication ## 2. Purchase and Assign Numbers Purchase new numbers or migrate existing ones to the configured SIP trunk within Twilio ## 3. Import Numbers into Retell AI In the Retell AI dashboard, navigate to the phone numbers section and provide : - Termination SIP URI: The URI configured during SIP trunk setup - Authentication Credentials: Username and password if applicable ## 4. Assign Voice Agents Create and customize your AI voice agents in Retell AI, then assign the imported phone numbers to handle inbound and outbound calls For a detailed step-by-step guide, check out the official Twilio integration documentation: [Twilio Setup Guide]() [(3) ]()

​ To learn more, see the sources I considered: [[1] How to Choose the Right Telephony System in 2024 | Retell AI](https://www.retellai.com/blog/how-to-choose-the-right-telephony-system-in-2024) [[2] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) [[3] Discord message from @artiombic on 2025-08-30](https://discord.com/channels/1186424376300679209/1186462578310910112/1411464530869092523) ​

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