can i switch phones?

i have a blue sprint phone on a plan, my brother has a seperate plan w/ a katona. he hasnt paid for it in like 2 months and some guy at this sprint place said its free to do it but he has to get his name off the phone, like has ot cancel his whole thing.. how can i transfer my # to his katona so i can use it instead of my blue phone?? whats the whole process of what i need to do?

Call customer service;
They can port your number to his phone, but not with any outstanding balances.