Nokia 6620 - Handset Volume Problems

Any input anyone can give me on this would be greatly appreciated -

My Nokia 6620 sounds great through any number of hands-free kits, but I
just cannot hear most callers clearly - or at all - with the handset. I
don't know - is this the result of dropping my phone one too many
times, or is not being able to hear the other caller commonplace with
the 6620? If anyone's had any similar experiences, please let me know.
If you've found a fix, even better.

Thanks,
-J