im trying to use an agent with a call transfer (co...
# ❓・ai-evy-supportk
K Rudy
04/10/2026, 5:37 PM@AI Evy im trying to use an agent with a call transfer (cold transfer, users number, sip invite) but i get an error;
{"status":"Transfer call cannot be completed, probably don't have the permission to perform the transfer.. Please inform the customer that the transfer did not go through and offer to try again or assist them directly."}
a
AI Evy
04/10/2026, 5:37 PMThanks for tagging me @K Rudy. I'll look through relevant sources and get back to you shortly.
AI Evy
04/10/2026, 5:37 PM### Answer
The "Transfer call cannot be completed, probably don't have the permission to perform the transfer" error typically indicates a telephony provider configuration issue rather than a Retell AI issue [(1) ]() [(2) ]() .
Based on similar cases, here are the most common causes:
1. Telephony Provider Permissions
Cold transfer using SIP INVITE with "User's Number" as caller ID requires your telephony provider to support caller ID override [(3) ]() [(4) ]() . For cold transfer, this uses SIP INVITE to establish the call path, and the provider must allow showing the user's number [(3) ]() .
2. Provider-Specific Requirements
- **Twilio**: Supports showing user's number on both warm and cold transfer [(3) ]() [(4) ]()
- **Telnyx**: May require verification of origination numbers or specific trunk settings [(2) ]()
- The error "Unverified origination number D51" has been seen with Telnyx configurations
3. SIP Trunk Configuration
If using custom telephony via SIP trunking, verify:
- Your termination URI is correctly configured [(5) ]() [(2) ]()
- Authentication credentials are set up properly [(2) ]()
- Your provider allows transfers to the de
AI Evy
04/10/2026, 5:37 PMstination number [(1) ]()
Recommended Actions:
1. Contact your telephony provider to confirm they support caller ID override for SIP INVITE cold transfers [(3) ]() [(1) ]()
2. Verify the destination number is in the correct E.164 format [(3) ]() [(4) ]()
3. Check your SIP trunk settings, particularly termination URI and authentication [(2) ]()
4. If using Telnyx, verify your origination numbers are verified
The issue is typically on the telephony provider side, not Retell AI [(1) ]() [(2) ]() .
AI Evy
04/10/2026, 5:37 PM
To learn more, see the sources I considered:
[[1] Warm transfer](https://discord.com/channels/1186424376300679209/1436106645632450671)
[[2] Transfer Call Permission Error - Need Configuration Assistance](https://discord.com/channels/1186424376300679209/1450235811470770359)
[[3] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call)
[[4] Call Transfer Node](https://docs.retellai.com/build/conversation-flow/call-transfer-node)
[[5] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony)
AI Evy
04/10/2026, 5:37 PMFeel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.