Why and When Twilio removes the error message from the receiver service?

Question

Trying to call an invalid number I found that when we use the Dial as normal to call a number like:

<Response>
    <Dial>
        <Number>3134610537</Number>
    </Dial>
</Response>

or

<Response>
    <Dial>
        3134610537
    </Dial>
</Response>

we can hear the error message from the provider telling as that the number is invalid or is not longer on service.

But when we use the url parameter inside of the Number tag we don't get that message:

<Response>
    <Dial>
        <Number url="http://a.url.here/">3134610537</Number>
    </Dial>
</Response>

I see the same problem using the REST API.

Why is that? And when does it happen?

Dial should be consistent with the REST API call, thought.

Answer 1

I submitted a support ticket in Twilio since this question doesn't have answers yet.

From Twilio Support:

That's a good question. That's one of the inconsistencies in the Twilio API with regards to "early media" or the audio the carrier sends before the call is connected.

With <Number url> Twilio plays fake ringing until the call recipient accepts the call, so the early audio is masked.

With REST API calls the early audio is not captured because the recording only begins when the call begins.

I'm sorry for the confusion and the inconsistency. Please let us know if you have any other questions.

Alex Chan

Twilio Customer Support

www.twilio.com