att address book network issue

My address/contact list hasn't been backed up for almost a year now, auto back up is on, and if I manually try it says that it will back up when I'm on a cell network. My phone IS on a cell network I make and receive calls, I'm in fact posting this on my data. So what is the problem? This doesn't only affect the very basic address book back up app. I tried to purchase an app in the app store by paying for it via my phone bill, but I can't because att,...the people I'm paying a monthly bill, wont let me access their network through....their network?!?!?!?!??!