My phone is starting to break down.. I have Nextel as my service provider, now my friend is going to give me his phone that he doesn't want any more because he's going to get a new phone. It's the Samsung Exclaim, and he has it under Sprint. It has Nextel walkie talkie but i don't know if i can use it on my Nextel service. Can i use my SIM card or something? I looked around and couldn't find the answer.