Hi, I think I found what the problem was!
Every time I had a call at the moment that I put the phone on my ear I used to close the screen from the power Botton on the side. I used to do the same thing with my Note 9.
When I stop using the side key to close the screen (it goes black by itself when I put it on my ear) while on a phone call it works fine. When I finish a call and take the phone away from my ear the screen wakes up and I can finish the call properly.
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