white iphone 4 16gb to swap for galaxy s2 or htc one !

I have an white iphone 4 16gb unlocked to all networks, brought 4 months ago from the apple store in southampton, come with headphones, charger, 2 cases only problem is that the box is a 4s box not a 4. Would like to swap for a s2 or a htc one, nee to be on o2 or unlocked, please text me if you haveany queries thank you.