[A little more specifically] I Currently have Att. I'm probably getting a Tmobile phone that is Unlocked for Att in a few days (I'm selling an Att iPhone 3Gs for an Unlocked Tmobile Mytouch Slide 3g and some cash because i need some extra $$$). At the moment i have an iPhone 3Gs with which Att requires an "iphone data plan" The phone that i will be getting from Tmobile will be an Android phone. For Att, if you have an Android phone, you need to switch from an "iPhone data plan", to a "smart phone data plan" How will i be able to do this without Att knowing im using an unlocked Tmobile phone? (Which im assuming is either illegal or if not illegal, definitely frowned upon.) If im wrong about phones from other carriers being unlocked and used for a different carrier is illegal or bad in any way please let me know. Any detailed answer or way to solve this issue would be greatly appreciated