That 503 error typically means there’s a connection issue between Vapi and Telnyx’s SIP trunk. It’s usually one of three things: your SIP credentials aren’t configured right in Vapi, outbound calling isn’t enabled on your Telnyx number/messaging profile, or there’s an IP whitelisting mismatch. Double-check your Telnyx SIP username and password in Vapi’s dashboard and make sure outbound is actually turned on for that number in Telnyx. Sometimes it’s just a simple config mismatch that’s easy to miss. The docs you’re following are right: https://docs.vapi.ai/telnyx If you’ve verified all that and it’s still throwing the error, I’m around to help dig into it with you , preferably we can hop on a call