BILLED FOR CANCELLED LINE

Please advise why I am getting hounded by debt collection agencies for a line I cancelled in 2016 at a premises I no longer reside at. The last company you had contact me sent me an account which showed no usage. Just because your paperwork and filling is incorrect you can't tell when I line is cancelled or not. If the line was not cancelled why would you wait 2 plus years to hand a customer over? Sounds like Telkom is trying to **** people.