V-numbers are from a type of auto-dialer called VDial. This software has been around for years. Collection agencies normally use it but I'm sure scammers are also using it to spoof a collection agency.
The string of numbers isn't random but translates into internal info for the agency, such as date, Zulu time, terminal ID of the employee, job control number, etc. A legitimate agency would need this info as evidence in a lawsuit. However, like I said, I'm sure scammers are also using VDial.