Hi.
I’ve had the same issue for a couple of years.
First on my iP12 PRO and now on my iP14 PRO.
It’s intermittent and it garbles the voice of the other person for both the caller and the receiver.
It sounds like the person you are talking to have dropped their phone into a glass of water and it only appears in phone calls (I have no recollection of the problem appearing during FaceTime calls or any other video/voice chat).
It affects the connection between my phone and my AirPods PRO (first gen).
And exhibits the exact same problem when I’m connected to my wife’s AirPods PRO or my 2023 Tesla.
If I switch the sound back and forth between my AirPods (or my car) and my phone it goes away but sometimes appears after a while again
Ive had my AirPods replaced twice (because of that other sound issue apple still fixes outside of warranty) and I have once done a DFU on my iP12 PRO setting it up as a new unit without restoring from my iCloud backup.
Ive been in contact with my service provider (just in case) but there is (of course) nothing wrong in their end).
If any of you also having the issue have found a solution, please post :)
Thank you :)