[KillaCamST]

I got a cell phone from a friend, the cell phone is with bell and has a spot in the back for a sim card. But when i put my sim card (Rogers) in the Bell phone, the old number still came up when i called my house phone. The Bell phone has been disconnected. So my question is, does the Bell phone need to be unlocked? Can I use my rogers sim card and still you the Bell cell phone with my old rogers number
?