Can I still keep my cell phone number after I switch providers?

in normal cases I know I can but it's a little more complicating. I have T-mobile right now and after I got back from vacation my bill was about $700! It turns out I was misinformed about certain charges and after speaking to about 8 different people from T-mobile, the only charge they took off was abut $15. I was told by a supervisor there's a monthly payment plan I can do to break down those payments then told otherwise today. There's no way I'm going to pay that money so I want to switch to Cingular/AT&T and keep my number. I don't mind if the name the account is under gets screwed up I just want to keep my number(my account with the new provider will be under a new name anyways). So is that possible in any way?