Telkom refusal to cancel my landline

I have been trying to cancel my Telkom landline and January. I sent the cancellation form via email and they tried to call me to discuss why one want to cancel it. I want available to take the call so they emailed me to say that they will phone back. Whether or not they called me back I don't know but I do know that I wanted it cancelled and they didn't cancel it. Surely, billing me every month for something I asked them to cancel cannot be legal! Incredibly annoyed with these large corporate bullies.