Q: Iphone 5 activation error

I just bought an used Iphone from a guy here in India.  The phone itself has not issues except it keeps on asking for activation.  I am able to activate the phone but get repeated activation messages.  The sim just works fine apart from the activation error now and then that I get and network fluctuation issues.  The phone had been purchased in USA - Verizon.  I did the IMEI search and found that the phone is an replacement.  Also, interesting is the fact that almost all the IMEI websites which are able to display details for free shows this phone as an 16 GB version, whereas I have a 64 GB phone.  There is something really wrong with this phone.  Can anybody help me as to the problem with the network and activation errors that I am getting.