Very Annoyed

I've been a loyal customer for 4 years with Telkom, no payment issues, no network issues nothing. This year I decided that I no longer want to continue with my contract so once it reaches the end I am going to cancel it, I went to the Menlyn branch on the 20/02/2023 and they said my contract is only due for upgrade not cancellation. I called on the 20/03/2023 and got it cancelled, telkom debited my account end of the month and I reversed because I did not understand why, then end of April they debited again and I called to under why and they explained the reason for the debit. I asked for a paid up letter and they said I should call on 17/05/2023. To my surprise today I receive a letter that my account has been handed over, I mean why? I have not received any call, sms nor email regarding an outstanding payment so how did they reach to a point of just handing me over whereas I don't even owe them? I am really annoyed as this is going to reflect very badly on my credit bureaus report.