Telkom charging me for service I cancelled, line was never installed yet they charge me

I app**** for a Telkom line online, after 2 months of waiting period I cancelled this application online. Just as this was done I received a phonecall from the technician ready to install, of which I declined and said I had cancelled. Then I started receiving Telkom bills. I contacted them and told them the line was never installed, I don't have this service. At some point the account was credited and balance brought to zero, the account should then have been closed. A few months later I start receiving the bills again, and once again I have to repeat the entire process. Then I receive a notification that my account has been handed over. Now Im explaining to these people what happened. Everything was done online yet they want proof from me that I have cancelled. How do I proof to them that I cancelled online and I cancelled over Telephone. Their lines are being recorded, right? So go back on my calls!!! They are forcing me to pay for service I never received!!! I will not pay and they will remove this bad debt from my name as it is affecting my credit status.