ok i have two iphones 1st gen and 3g, i uptade my old iphone to 2.1 w/o sim so i locked. to unlock it i had to activate with my 3g sim and now i trade my sim into the two phones and i only pay 20$dlls data plan for 3g.I'm afriad they notice that i used 3g thats why i used both phones. i went to att and to make sure my plan was ok and they said i have a ist gen iphone plan....try it you guys