A default against me without my knowledge

I cancelled my landline service with Telkom last year, and everything seemed to have gone smoothly, until now. I recently checked my credit score and discovered I have a default against me from Telkom, one which they had never communicated to me about either telephonically or electronically. It has obviously negatively affected my credit rating, and according to my knowledge of the CPA, what Telkom did in this instance is *******; ie to list an individual as defaulted without once contacting said individual to A) inform them of an outstanding amount, and B) inform them of impending legal action against them. I have since contacted Telkom to find out exactly how much I owe and why, and I see the invoice was from September 2019 (apparently a last bill after my service ended) for the amount of R265.73. I did manage to find the auto-generated invoice from Telkom in my email archive, so while they did in fact send it to me once, I was not expecting it and so must have simply passed it by. Obviously when I received no further communication from Telkom thereafter, in any form, I continued to assume the account paid up. I would like someone from Telkom to contact me ASAP to resolve this matter and to answer my questions as to why the CPA was not adhered to - or alternatively, why I am in error for thinking it should apply here? Of course I have now paid the R265.73.