Continuous harassment of an apparent account/s that are unpaid

This company keeps sending emails and harassing and threatening to blacklist me with City of Tshwane accounts that are not even mine. When you contact them they don't answer their phones and don't respond to emails or Whatsap messages. I have already spoken to City of Tshwane and issue was resolved but this company is still harassing me even after I informed them that the issue has been resolved.