CONTRACT CLOSED ,PAID UP LETTER NOT RECEIVED YET HANDED OVER TO THIRD PARTY

I had a contract with Telkom which I settled on in September 2021. On the 09th of September , I contacted the call center to request a paid up letter which I was given a case number ***4. To my surprise a debt collecting company contacted me and demanded proof of payment and paid up letter from me and said Telkom handed me over. I called the contact center again and was advised that the case logged in on the 09th f September was never assigned to anyone ,it was closed on the same day with no resolution. On the 11th of October the debt collecting company called me again and told them that I have not received the paid up letter from Telkom. I called the contact center again and was advised a new case will be logged ref no;***3. I went to Telkom store Musgrave Durban where I took the contract and was advised a manager will call me later. The manager called and said the debt collecting company must confirm payment first yet payment reflect on their side and will send an email as to why I have not received the paid up letter Eugenia Mchunu supervisor from the contact center in Johannesburg said he would call me at 11h00am which he did not do. I have not received any assistance and disappointed as to how I have been treated.