How can i fix my samsung d500??

Hi, i have the same problem where I get a black n white screen, i managed to get my phone to turn on to the main screen, everything looks and works normall e.g. signal and time, but the key pad does not work. I have to charge it up to switch it on, so not sure if its a battery problem?. Does anyone know what could be wrong with my phone, maybe the key pad? Its really annoying me!! cheers