Telkom doesn't want to cancel my landline! (Still billing me)

I am currently struggling to have my Telkom line cancelled. The issue has been going on since 18 September 2018, the day I logged my cancellation online. I even received a cancellation confirmation email right after completing the process.

Month after month, i'm still getting billed for the service, which by the way doesn't even work. I have endless email threads with their customer service people, who till this day won't let me speak to any manager.

I have stopped paying for the service deliberately and I fear It will have an impact on my credit score. Last month I received an email from their attorneys demanding payment. When I told them what's happening, they told me that they will close the file from their side and that they have notified telkom about my dispute.

I just need to know how can I leave this company once and for all.

Side note: I had a similar issue with my contract phone with them about 3 years back, took me 8 months to get the contract cancelled; And to be honest, they didn't cancel it because I still receive a bill, the only difference is that the mobile phone bill says R0.

We need to do something about this company, they are deliberately not letting unhappy clients go.