Telkom most useless accounts department and seevice

I have cancelled my ADSL in 2017 when I moved and didn't need the service since then and till now Telkom has billed me every month since 2017 and I can't get this off my name. I have had no product or service since then and Telkom has since then still billed me up to almost R5900 and they even confirmed that my service is cancelled and this is affecting my credit report negatively.