I am assuming you can’t even dial a number. Because, if you are able to dial a number that means you have a bad settings somewhere. I am also assuming that you tried to reset and reformat the phone and reinstalled all the software; if not, try that.

Normally if your input from touch is being ignored by the phone. That means there might be a hardware problem, that doesn’t necessary mean you have a bad screen nor dose it insure that you have a good screen. If this problem is new and it occurred after you dropped the phone or something I don’t know what the tell you.

It might or might not be your screen. But before buying a new screen, if you are confident enough, you should take the phone a part and reassemble it. That might solve the problem.

Sorry if this didn’t answer your question.