Since ATT's servers don't seem able to keep up, Apple should ask for your wireless number, billing zip code, and last four of your social. It should then ask if your contract is up this year. If yes, they sell the phone at the subsidized rate. They can inform you that they will check this info before they ship on the 24th, and if it doesn't match, they will give you the choice to cancel your order or agree to pay the unsubsidized rate.
Simple, right?
Simple, right?