To fix this, I suggest you try a Factory Reset of the phone. To do this, you need to have your phone turned OFF. Press and hold the Volume Up & Home buttons while you press the Power button until the Android logo appears on the screen. You should enter in the recovery mode of your device. Navigate using the Volume buttons and choose Wipe data / Factory reset option using the Home button. By doing this, you should know that you will wipe all your data from the phone and restore it to the factory settings. If this didn't help, try contacting a specialized service.