swap my blackberry 8900 for 8520 curve .

hi i wanna swap my blackberry curve 8900 for a blackberry curve 8520 must be fully working and in gd condition like mine plz no stolen phones or contract that will get blocked im only doing this has i have a upgrade and my lil sister wants a curve 8520 has she doesnt like the ball on this curve the phone is fully working open to all networks come and see and test .