Conveniently ignoring cancellation notice

On the 28th of July 2017 I sent a cancellation notice to Telkom for my adsl and internet service. I got a reply that my request will be addressed within 21 business days. Nothing happened. On Aug 28th I sent a second cancellation notice. Nothing happened. On Oct 4, I spoke to a Telkom agent on their customer service number and sent her copies of my cancellation notice. Nothing has happened. My latest invoice still reflects charges for internet and adsl, and on top of that Telkom is charging me for late payment. Really ...