Re: after a call is made, my screen display is switching off.
The screen should go dark when in a call and the phone is near your face. It should come back in a call when the phone isn't near your face, after about one second. It shouldn't go dark if you're not in a call. The usual problem is that the screen stays dark after you take the phone away from your face - that's a bad sensor or a screen protector interfering with the sensor.