Cannot activate verizon iphone 5

I am trying to activate verizon iPhone 5 in the iTunes and when it connects it gives me a page where I need to put verizon account information including phone number and last 4 digits of social security, but I do not have account with verizon and this iPhone I purchased from craigslist and it was(by sellers words) a replacement from apple. And as I know verizon iphones 5 are unlocked so I was going to send it to my sister overseas but I cannot activate it.

I did restore throught DFU mode and still same story, I need to fill in account info for verizon account. It might be somehow associated with somebodys account but how do I activate it?

Calle verizon and they say they don't have this imei number in the system to be associated with any account, apple said that it needs to be unlocked by verizon.

What to do? ESN seems to be clean.