### Answer --- This appears to be a known limitation related to how caller ID override interacts with extension dialing during transfers. The Issue: When using "User's Number" as the displayed caller ID, the transfer relies on specific telephony provider behavior. [(1) ]() [(2) ]() For cold transfers, it uses SIP REFER, and caller ID override depends on your telephony provider's support. This SIP REFER process may interfere with how extensions are transmitted. Potential Solutions: 1. Try "Keep raw input" option — In the transfer settings, selecting "Keep raw input" has helped some users with similar extension issues. [(3) ]() 2. Use Warm Transfer instead — Warm transfers use SIP DIAL rather than SIP REFER, which may handle extensions differently when combined with caller ID override. [(1) ]() [(2) ]() 3. Check your telephony provider configuration — The documentation notes that Retell Twilio numbers support showing user's number on both warm and cold transfer, while Retell Telnyx numbers only support this when using SIP REFER via cold transfer. If caller ID override is not fully supported by your provider, the transfer behavior may be inconsistent. 4. Verify extension format — Ensure the extension format is correct (must be 0-9, '*', '#', e.g.,

1234#

) . Note: There's an open discussion in the community about extension numbers not being included in transfer calls under certain conditions. [(3) ]() This may be a platform-level issu

e worth raising with Retell support directly.

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) [[2] Call Transfer Node](https://docs.retellai.com/build/conversation-flow/call-transfer-node) [[3] Call transfer extension number not working in call transfer node](https://discord.com/channels/1186424376300679209/1425942962810130452) ​

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