Okay, I want to get the 3GS. Another person on my family plan is eligible for an upgrade. I am not because I purchased the 3G the day it came out last year. Is it possible for them to get the 3GS and then I just swap their SIM card with mine? They already have a perfectly fine phone that's not an iPhone, so can they just put the card back in that without having to use my old 3G? Thanks for any help!