I haven't heard that sidekick will come under AT&T plan for more details contact AT&T ...However you can also use t-mobile sidekick mobile with AT&T after unlocking your sidekick mobile ....You can easily unlock your sidekick phone using sites like MobileUnlockSolutions.com they are providing unlock code for all mobile models at reliable cost ...After purchasing the code visit sites like MobileUnlockGuide.com to get free instruction about how to use that code and unlock your phone .