Cell phone company sucks/Buying a new cell phone?

So my cell phone plan is with Cingular/At&t. You know how they say Cingular/ At&t is the best? Well its not, a little FYI go with another company because the service sucks. I bought the first Blackjack back in July. Well when I first got it the Sync disc that came with it to install into my computer didn't work so I just didn't use it. Well recently I can't recieve mms messages and my phone won't charge with my charger, I have to switch out with the extra battery it came with. When I took it to the store they said "It could be water damage"(btw;; this is the second phone that they said "could be water damage"). So when I asked if I could just buy a phone and swap sim cards they said I couldn't do it until next March. Why am I paying so much for their service when A; the service sucks B; I have to go by their rules on when I can buy a phone? So I'm asking if anybody knows where I could buy a cell phone, because I am not waiting a whole year with this crappy phone.