Also worth noting...
If you buy online and set up your AT&T plan the cheapest voice plan you can get for 2 iPhones is a shared 700 minute plan that costs $70 per month.
When I signed up I asked if there was anything cheaper and they gave me a 550 minute plan for $60 per month.
So I basically saved $10 per month just by asking. If you don't think you need 700 minutes it's worth getting.
(If you can...I have no idea if they'll still do this since it was never on their website then or now.)
Call AT&T.
1+ or the AT&T website or AT&T Forum or AT&T store! it's only common sense.
Don't forget the $35 activation fee..