Hey, I will be travelling to San Francisco next week and will be bringing my factory unlocked iPhone 3GS with me. I have noticed that buying a GoPhone sim online will require me to purchase a phone along with it, so I have thought about buying an unactivated ATT GoPhone SIM on eBay for $5. Will buying the SIM, plugging it into my iPhone 3GS, and calling ATT to activate it when I arrive work? I have family there so I can ship the SIM to them, so that isn't a problem. I was wondering about data too- I will want to use GPS so I researched a bit and found that ATT has a $20 data plan for 100MB of data for prepaid GoPhones. Will I be able to add that? Thanks!