Phone overheating causing bugs.

My phone gets rather hot, not to the point of the heat warning popping up, but when listening to music via Bluetooth the song keep jittering or proceeds to skip the song. Also when on a phone call sometimes it glitches out and makes the weird dududududuududu noise and I can hear the person in the next end or they can’t hear me. I have realized the call not glitches out when a picture is taken or I load up a game app. I told this to my local phone fixers and they said it was the battery, so they changed the battery for me, yet same problem the back of the phone isn’t as hot but the side get really hot and the music keep jittering and the phone keeps bugging on calls and lags a lot. Someone please help.