yes of course, but you have to check if its unlocked ( meaning can use an carriers ). If its locked to verizon, u have no choice but to unlocked it ( i have no idea where ). for now, you can remove your t-mobile sim and put in to ur razr, see if it will work.
That depends on the unit. Is it locked / unlocked. You can check your unit first before buying it. If you already have the unit, try to remove your cingular SIM and put it in your Samsung.