so my mom gave me my sisters old phone when she got a new phone but my sister kepted the same number from her old phone. how do i activate her old phone and get a new phone number?

If you currently arent on the cell phone plan just go in with your mom and add your phone to the plane. If you currently have a cell phone plan and want to switch it to that phone you'll need to go to a verizon store to do a ESN change. You can do this over the phone but they charge you $20 to switch esn's while the store is free. After esn's are switched you'll reprogram the phone by dialing *228 then option 1. The phone will reset and you're good to make calls.

Call Verizon and tell them you have your sister's old phone and you need a new phone number. They should activate it.