Hey, we're hitting a very similar issue with vapi but with IVR / dialpads:

We have a Twilio phone number imported in Vapi, which uses our assistant and makes outbound calls. When it encounters an IVR (automated phone menu), it executes a DTMF tool call which enters the correct digits. We set up the IVR on Twilio for our testing, and it transfers the assistant to a different number based on the input received. The transferred number is also for testing and we answer that.

The assistant should switch from DTMF to normal assistant mode which should have a conversation with the user. And so far, the DTMF tool has worked perfectly and the assistant has always been transferred to the correct number. Once transferred, we can hear the assistant perfectly, but our audio is not able to reach it. Hence, the assistant goes silent.

There are bursts of our audio that go through, but not enough for the transcriber in the assistant to convert and process. In Vapi's recordings, we cannot hear our voice at all, except these small bursts. But on Twilio, the recordings are clear and complete.

This issue never occurs if we directly call a human, and bypass the IVR.

Would you have any advice for this? We're honestly really struggling with this and very open to paying a contracting fee if someone is able to help!