Big question. I am about to buy a phone from a friend of mine for a decent price and its locked under at&t. I use tmobile as a service and wanted to move my sidekick's simcard into the bb. Will I have to change my service plan for the phone? Like get a whole new plan based on the blackberry itself when I unlock the phone for tmobile? another question is will AIM MSN work on the blackberry curve if its from at&t and goin into a tmobile service? >.>