Harassment for an account that is not mine

This company has been harassing me for years for a Telkom account that is not mine. I have called. I have emailed. I have done affidavits. I have laid a charge at SAPS. Yet they keep going. How on earth do I make this stop?? They have told me they pulled the company records and they saw my name is not in the list of directors, yet a few months later the same story started. Who does one go to to report debt collectors?