I'm with Sprint and a friend gave me a Sprint phone. The phone uses a SIM card (didn't know Sprint had SIM). For some reason the phone still works. Does it work because it hasn't been turned off or is it because it operates off a SIM card? If so, my Sprint phone dosen't use a SIM. Can Sprint make me a SIM with my number and how much will it cost? If they can, do I still need to let the company know I'm switching phones or can I jus stick my SIM in the phone and it starts working?