Wireless Joint

I may have missed this but do you have to have a previous account with AT&T, such as a current phone line? Then you just add the post paid iPad plan? It doesn't sound like it from what I'm reading. I just want to make sure I understand everything correctly. If I do have an AT&T phone line, is it ...

Maybe i missed it, but do you already have to have a plan with AT&T, like a cell plan. Then you just add the post paid plan too it for the Ipad? Doesn't sound like it but i wanted to confirm.