Poor agent and company service

I want to know how your Agent(Kevin) verifies collections based of the data that is given to them?

This agent had called me today asking me on an account that has been paid last year. I owe MTN and no one else NOTHING!!

This is super frustrating to be taking calls everyday from different companies regarding an account that's closed. Can I get answers as to why you are contacting me

Based on what information are you calling me for?

And if you tell me based on information from MTN then you guys certainly use old information.