Any Phone company's offer part ex on contracts?

[forspinki]

I'm looking to get iPhone4 but I wana find somewhere I can trade my iPhone 3G for some of the contract already paid off or something

 

[T0MMY]

Am sure only O2 does part exchange but it had to be on a 12 months contract. Am not 100% maybe all contracts however if the iphone 3g you had was on orange they will not accept.

 

[JealY]

Just sell it.