TELKOM Accounts Pay for a Cancelled Line

I cancelled my domestic fixed line rental with Telkom in August 2018. This was done online. Telkom acknowledged the cancellation by email, with a reference number confirming the cancellation. Telkom continued to bill me for line rental. I contacted Telkom, in an email dated 19 January 2019 Telkom acknowledged my line rental cancellation but also referred my account to the dispute section. Telkom handed my account over to Alpha Collections. Alpa collections are now harassing me. It is obvious that Telkom accounts is dysfunctional regarding this matter. Telkom please urgently correct this matter.