Hoping somebody can tell me if this won't work: My friend is eligible for the 3GS upgrade, but was only going to buy the 3G. She has offered to buy the 3GS and sell it to me for her upgrade price, and I would give her my 3G. I'm thinking (based on threads here) that I can just put my old 3G sim card into her 3GS, and put the 3GS sim card into my 3G and give it to her. That should preserve phone numbers, etc.? Would I need to re-activate? Thanks for any comments or advice.