Telkom wrongly handed me over to debt collectors

I have been handed over to debt collectors because Telkom kept on billing me after I have canceled my ADSL line. I have canceled my Telkom line and ADSL on the 20th of March 2018. I have also gone on the 23rd of March to the Telkom shop in Woodlands mall to ask them if this is correct and the personnel gave me the same form to fill in again. She said that I would receive a call from Telkom in 21 business days to say my line will be closed. Telkom technicians came in that period to my house to make sure everything is canceled. I have not then heard from Telkom until I called them in August to ask why they kept on billing me after the cancellation. The operator said that there was an error on their side (the IT department) and that they will fix everything for me. I did not hear anything again from Telkom until the debt-in debt collectors started calling me in January and harassing me on money that I do not owe Telkom. I called Telkom again and they said that they see that I canceled in March 2018 and that they will sort it out. Well, it is now over a month and still nothing. I called them 3 times after that phone call and they kept on saying that it has not been handled.

What can we do stop this *********** behavior from Telkom? This is a recurring theme from this company as I know about more people than I can count that have these same type of problems. The worst thing about this is that Telkom all the other useless state SOEs and political parties just don't care. Should I keep on waiting and hoping that someone competent will help me?