On the AT&T network I get about 5% of my calls to connect but then I only hear silence while the other end hears me. In this case I believe it's a network issue and not a phone issue because it has been doing these for four generations of cell phones so far.
Wow, I'm surprised you've never had to do a hard reset on your phone before. The need to do that is infrequent, but most smartphone owners I know have had to do it at least once, with one exception -- iPhone owners, who can't easily remove the battery anyway. But even there, Apple provides a different way to do a hard reset.