AI Agent reads back incorrect first digit of phone number

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1

Call ID: call_7f8725917bc0954c3b02c587d6e

Dynamic variable has lead number as +15202267101
Agent reads back number to caller as: 45202267101 - so it changes only the first digit from 5 to 4.

2

Here is another call where the agent makes up a number and does not repeat what is stored in the dynamic variable: call_7ab185bdd76f0f5c335b8a351d3

3

Hi @skhandor

Can you share which LLM model are you using ?

Thank You

4

I am using open ai 4.1

5

Hi @skhandor

Thank you for providing the call ID. I’ve shared it with our team for review.

We’ll keep you updated as soon as we have more information.

Best regards

6

Hi @skhandor

Team checked both Call IDs ,we confirmed the issue in both calls.

The root cause is that GPT-4.1 misreads the phone number when it includes the +1 country code prefix. The “+” symbol in the E.164 format (+1XXXXXXXXXX) causes the model to output incorrect digits when reading the number back.

The recommended fix is to strip the +1 prefix from the lead_number before passing it as a dynamic variable. Instead of sending +15202267101, send just 5202267101 (the 10-digit number). This works, as seen in your second call where the agent repeated the 10-digit number correctly.

You can do this by formatting the number server-side in your webhook response or by adding a prompt instruction like: “When reading back phone numbers, only read the 10 digits after the country code. Do not include +1.”

Either approach should resolve the issue immediately.

Thank You

7

Thanks, will try that out!

8

Ok, we have done that and we just found another call where the agent changed only the first number.

call_b33d503a31993c9799024574bfd

Dynamic Variable: lead_number:6474062750

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image517×151 11.9 KB

Here are some more call ids with the same issue:

call_58bf61b47adb2b592ac8fe2360a
call_34c3aab7b7c8ee91794c3d33e27

9

Hi @skhandor

Your issue has been already passed on to our team for further review.