Not sure if anyone can answer this, but here it goes: I'm on an AT&T family plan, and bought an iPhone 3G last year at launch for full price ($499). My phone says I'm eligible to upgrade in August, so supposedly I can purchase a new iPhone on Friday for the discounted $199. Question is, will I be able to keep my 3G to give to another member on my family plan? Or do I have to trade in the 3G? Thanks in advance!