Telkom - Billed for a service which was cancelled almost 2 years ago

Telkom please can you update your system properly! I have been called by multiple debt collection companies for money monies owed. I have cancelled my account twice and still haven't got it right. My account at the time was paid in full and still getting billed for a service I haven't had in almost two years. I refuse to pay for a service which I cancelled. I have jumped through all your "hoops" to cancel the ADSL and telephone line service twice and still haven't got it right.

Who do I need to talk to stop this harassment now. Kindly help me as this whole thing is starting to take strain on my mental health.

Thank you Steve