### Answer The

invalid_destination

disconnection reason indicates the destination phone number is invalid. [(1) ]() Here are steps to troubleshoot: 1. Check the call history and detailed log — it contains the disconnection reason, SIP error code, and error message which should help identify the root cause. 2. Verify your SIP trunk configuration: - Double check your configuration and make sure you imported the right information. - Check your Termination SIP URI for any spaces and remove them. [(2) ]() - Use a localized termination URI near your region. - Verify your username and credentials are correct (the username is different from the friendly name) . - If the configuration is not correct, delete the imported number and re-import. [(1) ]() 3. Check with Twilio: - If the above doesn't solve it, check with your telephony provider (Twilio) to see what's the error on their side. - Also check the logs in your telephony provider. [(3) ]() 4. Verify destination number format: - Ensure the destination number is in E.164 format (+country code, then number with no space, no special characters) . [(4) ]() 5. Check international dialing permissions: - If dialing internationally, search "geo" in Twilio to find the "Voice Geographic Permissions" setting. [(2) ]()

​ To learn more, see the sources I considered: [[1] Debug outbound connection issues](https://docs.retellai.com/reliability/debug-outbound-call) [[2] I’m trying to use a toll-free number (connected from Twilio through a SIP trunk)](https://retell.discourse.group/t/i-m-trying-to-use-a-toll-free-number-connected-from-twilio-through-a-sip-trunk/127) [[3] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) [[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.