iphone 4 for sale on t mobile or swap for unlocked blackberry 9900 ?

Iphone 4 for sale on the 3 network,,,in excellent condition,,only 1 tiny mark on it,,,would consider swapping for an unlocked blackberry 9900 or 1 that is on the 3 network.. Bought this for my daughters 13th birthday but she prefers the blackberry.. Thanks for looking,,,,,