I cancelled my Telkom line, but I'm still being billed and harassed by the consultants

had an account with Telkom years ago. My account number at the time was ***I called in to cancel this account and the consultant who assisted me said all is in order. I was surprised to get a call from Telkom notifying me that I have an account in arrears. The account accumulated because their consultant did not do a proper job now. Strangely, the account accumulated even though the line was disconnected. I am listed as a bad payer in Credit Bureau. I got numerous calls from Telkom Consultants and I have been explaining the same this to them. When asking to speak to a relevant person. I have been sent from pillar to post. Consultant keep on telling me that they will escalate and nothing happens