I have a Razr Maxx on verizon that is grandfathered on the unlimited data plan and I am ready to get a new phone. Upgrading through verizon will cause me to lose the unlimited data so my plan is to buy an S6 on ebay or somewhere like that. My question is: what is involved in changing out phones? Is it just a matter of swapping out the SIM or do I have to go into a verizon store? Is there anything I should be aware of? Do I need to buy an unlocked phone? Thanks in advance for any advice.