### Answer --- This is a phone system routing issue rather than a Retell configuration issue. The problem is that your client's phone number has call forwarding enabled to your Retell agent, so when you transfer back to that same number, the forwarding kicks in and routes it right back to the agent. [(1) ]() The solution requires changes on your client's phone system side: You need to work with whoever manages your client's phone system to set up direct lines or extensions that bypass the forwarding rule. A few options to discuss with their phone system provider: - Get direct extension numbers for departments/people that don't route through the main forwarded line - Set up a SIP trunk where you can pass calls directly to specific extensions - Configure the phone system to recognize calls from the Retell number and not apply forwarding to those One user dealing with this exact scenario mentioned their phone provider (Key2) could support SIP URI with direct extension routing if they had a static IP and proper trunk configuration. In short: Ask your client's phone system administrator to provide direct numbers or extensions for transfer destinations that won't trigger the forwarding rule back to your agent.

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

​ To learn more, see the sources I considered: [[1] Hi team, I’m having trouble with the transfer_call function.](https://discord.com/channels/1186424376300679209/1384634772772360383) ​

### Answer --- Whether the call lands on the extension or gets forwarded back to your agent depends entirely on how your client's phone system handles the forwarding rule, not on Retell's transfer configuration. When you set up a transfer in Retell, you can specify the transfer number in e.164 format and include an extension using digits 0-9,

*

,

#

(e.g.,

123#

) . [(1) ]() However, the key issue is this: if your client's phone system has a blanket forwarding rule on the main number that routes all incoming calls to your Retell agent, then transferring to that same number (even with an extension) will likely trigger the forwarding before the extension can be processed. What you should ask your client's phone system administrator: - Can the forwarding rule be configured to not apply to calls coming from the Retell number/SIP trunk? - Can they provide a direct line or SIP URI to specific extensions that bypasses the main number's forwarding? [(2) ]() One user in a similar situation was told by their phone provider that they could support SIP URI with direct extension routing if a static IP and proper trunk configuration were set up. In short: Retell can send the extension digits, but your client's phone system needs to be configured to actually route those calls to the extension rather than applying the forwarding rule first.

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) [[2] Hi team, I’m having trouble with the transfer_call function.](https://discord.com/channels/1186424376300679209/1384634772772360383) ​

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