Cancelled Telkom account, still being billed.

Cancelled my Telkom account in July 2018, received confirmation of the cancellation and had to pay for an additional month for the cancellation to go-trough. In September Telkom started to bill me again and have done so ever since. Logged disputes without any response, lately unable to log any response. Telkom has recently handed me over to dept collectors and still unable to get a response from them. I just want to cancel my account and keep it cancelled without being blacklisted. Please can Telkom please sort this out.