I bought my Sony a while ago, but lately it has been having this really annoying problem. Whenever I lock the phone it works well however, when I come to unlock it, I press the power button and only the screen lights up with nothing on it. This also happens when I call someone, the screen turns off and immediately disconnects the call. I have tried nearly everything, the power + volume button as well as hard and soft resets, any help is much appreciated 
