Telkom ripping ex customer off

It seems that it is impossible to cancel an account with Telkom. I relocated out of the country in April 2018 and subsequently made attempts to cancel my account online. When this proved fruitless, I went to their shop in June 2018 when I was in the country. And they assisted me with the cancellation. Yet, despite that, I am still being billed. For what? Honestly, I am not prepared to pay for somebody's incompetence