Hi, I've seen some iPhone 4's on ebay that are advertised as new/unused and never plugged into itunes. Does the warranty begin when a SIM card is added and first used on ATT network? Or do you have to contact apple to activate the warranty? What should I be aware of when buying from ebay vs. apple store? My iphone 3g died, I'm off contract, and do not want to get back on contract? If I buy iphone 4 do i just cut the sim on my 3g down to microsim size and insert? Thanks.