### Answer The "user is busy" / 468 error on inbound typically means the call isn't reaching Retell properly. Here are the key things to verify in your Telnyx Elastic SIP Trunk setup: 1. Confirm the FQDN is set correctly [(1) ]() Add Retell's SIP server as the FQDN:

sip.retellai.com

with DNS record type set to

SRV

. 2. Verify Inbound Settings - Number format:

+E.164

- Codec:

G722

,

G729

,

OPUS

- Transport method:

TCP

(UDP is temporarily not supported due to a connectivity issue) - Select your SIP region 3. Check your account status [(2) ]() One user resolved a similar "busy" issue because they were on a Telnyx trial account and needed to upgrade to a paid plan. 4. Ensure the number is imported to Retell [(1) ]() After setting up the SIP trunk, you need to import the number to Retell so it knows how to route the call. Supply Telnyx's FQDN as the termination SIP URI (e.g.,

sip.telnyx.com

based on your SIP region) , along with the username/password from your outbound authentication setup. If everything looks correct and it still doesn't work, can you share a call ID or pcap file from Telnyx? That would help narrow down where the routing is failing.

​ To learn more, see the sources I considered: [[1] Telnyx](https://docs.retellai.com/deploy/telnyx) [[2] [TELNYX/RETELL] SIP Configuration not working even if I followed Retell.ai documentation](https://discord.com/channels/1186424376300679209/1404046661918920735) ​

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