Transfer call issue - complains about E164 formatting when it's valid

Support Help
1

Hi, We’re getting issue where our call transfer sometimes fails, it is bizarre and rare because the complain message makes no sense. The detailed logs provide no help, and I see no error on the Twilio side, so it appears to just be internal to Retell’s validation efforts.

Basically, most of the time transferring to this number works, I blanked replaced the middle 3 numbers with X, but it is a valid e164 number, and it is the number we have configured, and it is a number we have successfully transferred to multiple times.

Sometimes, rarely, it would trigger this response - and we’re not sure how we can fix anything on our end, since the error message is wrong.

Call ID call_b8b896c1d041083100159265d86

tool_call_id: cc7e0bad3a44f2e5

{
  "execution_message": "I’ll connect you now with our [Location] team so they can assist you and take a message for [Name].",
  "transfer_destination_number": "+1954XXX9383",  * I edited this, XXX were 3 numbers, it is the valid, configured number *
  "transfer_number_extension": ""
}


{"status":"Error transferring: Transfer destination number is not a valid e.164 number"}
2

This intermittent E.164 validation error on valid numbers is a known issue that other users have reported(1)(2)(3).

The error message “Transfer destination number is not a valid e.164 number” appears even when the number is correctly formatted and has successfully transferred in other calls(3). This indicates the internal validator is failing intermittently rather than the number actually being invalid(3).

What’s been observed:

The same destination number can fail validation in one call but succeed in another call with identical configuration(3). This inconsistent behavior suggests the validator is misinterpreting the input string in specific scenarios(3).

Potential workarounds to try:

  1. Check your Displayed Caller ID setting in the transfer configuration - some users found changing this setting helped with transfer issues(3)

  2. Verify your Termination URI is correctly configured to point to your provider’s URI (not Retell’s URI)(4)

  3. If using Dynamic Routing, ensure it’s properly configured - one user reported this feature resolved their intermittent E.164 errors(2)

For immediate support:

Since this appears to be an internal validation issue that Retell needs to investigate, I recommend:

When contacting support, provide your Call ID (call_b8b896c1d041083100159265d86) and emphasize that the number works successfully in most calls, which proves it’s valid E.164 format(3).

3

Can I get an engineering team response on the estimated time for fixing this, and if there is a ticket I can follow. Our clients are complaining, and if this is a sustained issue we might have to switch providers.

4

Hello @nicholas
The team is pushing a fix for this right now.