Is any personal information needed when doing this method? If so, is its accuracy ever checked? Do you need any money to spend to execute this method? You mention that the VCCs you get are free, but is any sort of upfront payment necessary?

About the phone numbers, what carrier are they registered under? Are they like the free text apps such as Pinger which are incompatible with some services or real numbers registered under major carriers such as AT&T, Verizon, etc.