Apple Iphone 3g black on 02 sale or swap +

I am selling my iphone 3g due to upgrade, it works 100% fine with no issues, it is on the IOS 4.2.1 and come complete with a charger. There are some marks on the back of the phone and on the screen but this no way effects in how it works. I would sell or swap for an ANDROID phone. NO timewaisters