I am in the same boat as you and my solution is through personal experience with ma bell's crappy customer service.
Originally Posted by cpc12
Most important step is to cancel your current data plan through the ipad. The data plans are not feature plans so you must cancel it otherwise att will continue to bill you for two data plans which they did to me when I replaced my old ipad.
Wipe clean the current ipad2 - settings, google or search forums on how to prep an idevice for sale then get rid of and wait for the new ipad to arrive and activate a new plan. Additionally, 4G/3G data is billed together so there's no need to select which data you want....they're all pretty much now called 4G anyway. 14.99 will still get you the same 250MB on ATT...just be mindful that in the LTE, you can suck that data up in no time.