If you have an iPhone and your screen goes black during phone calls, it's probably annoying you to death. This Simple How-to Guide will show you how easily you can fix the problem yourself, and you won't even have to stand in those long lines at the Apple store to do it.{googleads} 

iPhone Screen Goes Black During Phone Call

A Description of This iPhone Screen Problem :

During phone calls the iPhone screen would go black which would prevent me from accessing the speakerphone, accessing the keypad and even accessing the end call button. One of my biggest problems with this issue was that I had no idea why it was happening and I wondered if my new iPhone 4s was broken.

Can you imagine calling somewhere where you have a digital voice menu that requires you to press numbers and everytime you try to press a number the iPhone screen shuts off? Yeah, it was pretty annoying but luckily I finally found a solution for my phone and hopefully this simple solution will fix your problem with the proximity sensor.
The proximity sensor is responsible for shutting off your screen so that your face would not face-dial or hang up on who ever your talking to. What happened in my situation was that my proximity sensor was being triggered even if my face was not anywhere near the phone.

After reading up about the iPhone and the proximity sensor I quickly realized that my OtterBox Defender case was either deformed (bought it on Ebay) or made wrong. So I grabbed a pair of sharp nose hair clipper scissors and cut off the little piece of rubber between the eyelets for the speaker and the proximity sensor and Whala! The problem disappeared for good and my iPhone is back to being my faithful companion and assistant again.

Here's a How-to Guide that will show you exactly how I fixed the problem.