[lamnk]

But is the old contract still in effect ? If yes, then the profit selling his old phone probably doesn't cover the money he must paid for one year left of the old contract. That's why i'm confused.

[tylerhowarth]

Why would you have two contracts?

Buy iPhone 3GS June 2009, Contract ends in June 2011. June 2010, sell 3GS, buy iPhone 4 and now contract ends 2012.

It is an early upgrade which requires you to sign a new two-year contract.

[whimsy]

Effectively, the contract's life is "reset" to two years.