What happens if you have a grandfathered unlimited plan on ATT. The plans offered on the upgrade page seem to be only Next plans.
I'm guessing that I'll be forced to pay full price.
Couldn't you just add the new iPhone Upgrade Program phone to your account as a new line, swap your SIMs and then cancel the new line? The new line is just a "bring your own device, no contract" line so you'd be out the activation fee and whatever the prorated amount is for the number of days you kept the additional line on your account.