I might be purchasing a Thunderbolt from somebody on Craigslist. They have used their upgrade to purchase and activate the phone on their line but it now has been deactivated to sell. If I purchase and try to activate on my line, will I run into any problems? Normally I would go onto My Verizon and use that to activate it. Would I do the same thing or would it be different because of the 4g Sim card? Thanks for the help!