The Associated Press reports that AT&T is quietly offering unlimited iPhone data plans to some iPhone customers despite having killed off its unlimited plan last year. AT&T discontinued its unlimited smartphone data plan this past June and switched to a capped structure, offering users 2GB of data each month for $25 or 250MB of data for $15. At that time, customers with $30 unlimited data plans we’re allowed to keep their plans or switch to one of the new, less expensive plans. According to the AP report, customers who opted to switch from the old unlimited plan to a new capped plan are now being given the option to switch back — presumably as part of a larger effort to dissuade would-be defectors. Verizon Wireless will release the iPhone 4 next month, and the carrier confirmed its plans offer unlimited data for a limited time at launch.