I press button with my face while making ph.calls
When I call friends and family and hold the phone close to my face, i inadvertently keep on pressing mute button or speaker button with my ear or face which is very annoying. My understanding is that there is a proximity sensor in the iphone and I have seen my friends phone and their screen becomes black once the phone gets close to their face. Mine does not
Humayon B khan
You might want to check the ribbon cable connection 3. This connects the proximity sensor. The connector is called a ZIF connector, and has a special way of opening it. you should look for info on how to open it (basically flipping up a lever, and gently pulling or pushing the ribbon cable out.) Be careful, the internet is full of stories of people breaking the connector. it's a pain to replace.
Make sure that the connection is firmly/deeply in before flipping the lever back down.
hope this helps.