Seems really strange. Have you installed any 3rd party home screen-changer or something similar? Since the service center tests the phone before sending it back to you it feels like there might be something you've installed on the phone. I doubt the service center would make the mistake and letting the phone back to you broken three times.
Have you tried running your phone in safe mode for a day or so? That's the easiest way to determinate if the problem is related to the phone/screen itself or something you've installed. To start the phone in safe mode you press volume down when starting the phone up. You have to keep pressing the volume down button until the phone gives you an extra vibration to indicate it's starting in safe mode. You will also have a small text-box in the bottom left corner saying "safe mode".
