Can i transfer an iphone from sprint to virgin Mobil?

My friend has an iPhone 4S, and i'm going over to virgin mobil; can i use his Phone as mine on virgin mobil or do i have to buy a whole new Phone?

Take it to an unlocking service to get that done. Virgin and sprint use the same service so it's possible.

Unlocking your phone yourself is really complicated. Calling and texting is easy, data is the hard part.