My question is can I add a pre-owned phone to my Verizon line?! can I swap or change my phone to my line? lets say I already have a phone with Verizon and a friend gives me their old Verizon phone to keep. Can I go to the Verizon store and tell them I want them to change my line to the new phone I have and that I no longer want to keep using my current phone? and if it is possible is it free of charge?!