My wife and I both have iPhone 3G phones (and have since July 08). The speaker in my iphone is dead and I have tried everything online to fix short of opening the iPhone. My wife is eligible for the $199 upgrade to the 3GS but I am not and have to wait until March 2010 or pay $399 now. If I upgrade her line to the iPhone 3GS (for $199 and new 2-year contract of course), can I use the new iPhone 3GS instead of her by just simply using my sim card from my current 3G (with the bad speaker) and restoring a backup from iTunes when the 3GS arrives? And no, she does not care - I have already asked her. My main question is just if there is any way AT&T ties the online account info on hardware with the sim card to where if it shows that I should be using the 3G and not the 3GS if we will have any problems. I don't think there will be any problems, but I need much more expert advice. Thanks.