CELL C PAID-UP LETTER STRUGGLE

I have been requesting a paid letter from cell c since I paid off my account on the 7th of January 2022. I paid off the balance that existed on my cell c account on the 7th of January. A week later, I was told the payment is still not reflecting. I took a look at my POP and realized that I had made a mistake with the beneficiary ref number, requested that they fix it and allocate on the 13th of January and received SMS confirmation that the case was closed. But l still did not get my paid up letter. I called in again to request the paid up letter but the collections consultant said the payment was not reflecting on her side and she could not help me, I asked her to check the case number *** and she confirmed to the case being closed and referred me back to customer care and the guy tried to put everything on me that all this would not have happened had I not mixed up the ref numbers. It is the 18th today and I still don't have my paid up letter regardless of receiving the SMS that case was closed. I WANT MY PAID UP LETTER. There shouldn't even be a balance on this account but you are dragging your feet updating and closing this account.