Shocking, disgusting service from MTN

I took a contract with MTN in 2018, which was a 24 month contract. At the end of the 24 month period which was in 2020, I cancelled the contract with them telephonically in 2020. After more than a year I received a call from a debt collector advising me that I owe MTN over R2000.00 due to the fact that when you cancel a contact with MTN and do not renew a cancellation fee applies. This was not mentioned to me and should there had been a cancellation fee applicable they could of taken it off with my last debit order. I want an explanation from MTN regarding this cancellation fee and will not be paying an amount of R2000.00 to cancel a contract that I paid R439.00 per month for over 24 months. Please also just keep in mind that the sim card received with the contract was never even utilized. Should a cancellation fee be applicable, I am happy to pay the cancellation fee provided that I am only charged what the cancellation fee was originally and nothing more. I would like an explanation from MTN as to why for the last year before handing over to the Attorneys, I was not even notified of an outstanding amount on my account. According to my credit profile the account is also closed. I am absolutely shocked and disgusted in the way this query has been handled and to not even advise me that they were handing me over till over a year later is completely shocking. Once I receive an explanation from MTN and only the balance due for the cancellation fee, I will make sure that the account is settled. I have tried to call your call centre but have not been able to make contact with a consultant who is able to assist me.