Why does it take 10 days to issue a paid up letter

I had a cellphone contract with Telkom, when 24 months was finished I went to the shop and ask them to convert my number to prepaid and cancel the contract, they agreed, month end they debit my account, the following month end, they debit again, I ask them why they say my contract is now on month to month, how so after the 24 months has lapsed and I canceled, then I reversed my money and blocked them from debiting my account, they called I told them they’re not getting a cent from me. I recently found out they went ahead and blacklisted me, I called them two weeks ago and they say I owe R178 that is why they are blacklisting me, I got sick of arguing and paid the R178, then they tell me it takes 48hours for them to confirm that they received the money, 48 hours later I call them they say it takes a further 72 hours to allocate the case to a person, 72 hours later I call, now they are saying my case has not been allocated to anyone and it takes 7 days to issue a paid up later. I am sooo ****ed because, I don’t understand why a 24 months contract must go on over 24 months, on top of that I have paid Telkom two weeks ago what is difficult with issuing the paid up letter