Telkom - worst service ever!!!

I was sold a 50 gig broadband deal after being told by the sales consultant that it would be more than enough to run my business admin from home as well as to stream Netflix etc. Half way through the month this was depleted. We contacted Telkom and complained about this but stupidly upgraded to the fiber line still with Telkom. We naturally asked for the broadband to be cancelled. No problem, or so it seemed. I was told it was cancelled, never told about any penalties I would incur. This was done in February. After months of still being debited i eventually was told that it was for the cost of the modem, I accepted this. On the final payment i was told i now had a 0 balance. I must add that I have numerous reference numbers that were sent via SMS confirming cancellation. I sent requests via the online portal, via telephone and via E Mail. Even sent a mail thanking the last person who helped me, who confirmed it was definitely canceled and stood on a 0 balance a thank you mail and received a mail confirmation back from him. Even after this mail i was still being debited, March, April, May, June, July and so on. Imagine my surprise when i received a call from a collection agency threatening me with legal action if i do not pay a further R1146.40 that is being claimed from me. I sent her all the documentation i had, all the SMS messages, including the screen shots of the online portal cancellation confirming that the service was cancelled, only to be told that this was not acceptable and that without a letter or E Mail from Telkom that stated in writing that the service was cancelled that they would then proceed with legal action to recover the money. I told her to then go ahead because i was not going to pay another cent. Its clear to me that Telkom and its staff do not know what one department is doing and that the staff who claim to be helping you are nothing more than a joke since i'm told that they never did the actual cancellation. Why then is this my problem???