You can often bypass any Call Endpoint (Buyer) IVR by using Retreaver to send DTMF tones (key presses) on behalf of the caller.
Once on the Edit screen for your Call Endpoint (Buyer), near the top, you will find the field for Send Digits. In this field, use the letter w to represent a 0.5-second pause. You may find that entering ww1 works for you, but it all depends on the unique IVR. You may find that when you place a test call that it doesn't seem to work. Try adding a w and try a test call again. This trial and error is how you arrive at the minimal pause before the system will allow a key press to be accepted.
We have encountered Call Endpoint (Buyer) IVR systems that allowed multiple key presses. Such as www1www2.
We have even encountered an IVR that required a Zip code entry. This use case ended up using www1wwwww90210 in order to bypass this. Since every IVR is different, this will always require a couple test calls to get just right.
Callers will continue to hear ringing or music-on-hold while the key presses are being processed, they will not hear any beeping as Retreaver bypasses the IVR.