It's actually worse than this article states. If you get the "AT&T Next 24" plan that just means you can upgrade to a new phone after 24 months. You are actually agreeing to make 30 payments so you end up with $56 tax plus $29 x 30 or $926.

Edit: Also note that you are only eligible for upgrading after 24 months if your phone is in good condition--no cracks, chips, etc. If your phone breaks not only do you have to buy a new one, but you have to keep paying for the old one for 30 months!