Hello
Import the number via Elastic SIP trunking — set up SIP trunking with their telephony provider (Twilio, Telnyx, Vonage, etc.), point the number to Retell’s SIP server sip:sip.retellai.com, then import it to Retell and bind your agent.
For more details you can see our (Custom Telephony Overview - Retell AI) Guide.
Thank You