Telkom - Landline Cancelling Bullying - Affect Customers Credit Record

I had cancelled my landline about a year ago via the Telkom website. You do not see the option but you have register an account and then login to cancel. It showed that the cancellation was successful. However now after so long they do not communicate with me to let me know that there is a settlement for the cancellation but they take me straight to the debt collectors and credit bureau. I have since paid the amount which I am not sure is even correct. This is bulling of consumers and should not be allowed.