blackberry bold 9900 for sale or swap for an iphone 4(may ad cash for the right phone) ?

the phone is only a few months old,it is in mint condition,it is on the vodafone network,it comes with the box,leather blackberry case,charger,headphones etc,i would like an iphone 4,the reason for sale is i dont use bbm etc so no point in keeping it,thanks for looking