Chosen Solution
We changed the screen on an iphone 8 plus and after the replacement the phone always turns off when i try to call anyone. everythin else is working fine
Chances are whoever changed the screen damaged the front camera (specifically on the proximity sensor) which causes this issue. The front camera assembly would need to be replaced. I have provided links to guide on how to replace and parts if needed from iFixit. iPhone 8 Plus Front Camera and Sensor Cable iPhone 8 Plus Front Camera and Sensor Cable Replacement
