[stevenwei]

I think you need to differentiate between unlocking the phone and breaking the service contract. Just because you want the former doesn't necessarily mean you want the latter.

For example, you might want to make sure your phone is unlocked so when you take a week trip overseas you can pop in another sim card to use in another country, but you might keep your existing contract with AT&T active because you'll keep using it when you come home.

I don't really see any logical reason why having a service contract with a cell company should prevent you from doing this.