Totally Unacceptable Service from Retentions, Customer Care & "Back Office"

I paid up my Vodacom account on the 21st of June 2019. I sent proof of payment, my ID Copy and invoice to *** and *** as instructed by one of the agents. I then called the Retentions/Cancellations department as advised, to inform them that I’ve made payment and sent the necessary documents they requested. I was then told that their Back-office team will action, and the account will be closed within 3 – 7 working days. I was shocked to learn this past Saturday (09 November) that the account is open and active. I was then put through the Retentions department again to get this resolved and after numerous calls, email and back-and forth Yassen called me on Sunday the 10th and assured my that they will rectify all the records, do necessary reversals and close the account. I acknowledged his response and requested to a paid-up letter to be issued so that I can clear my name with the Credit Bureau. Instead of Yaseen responding, a lady by the name Nandipha called me on Monday the 11th and told me that Back Office is working on it. I followed up on Tuesday the 12th, now another lady by the name Gugu called me and told me that Back Office is still working on it. I have been chasing up endlessly with no results. Who on earth is this "Back Office" because it is clearly non-functional. I don’t know what else to do to get this paid up letter. I need it as a matter of urgency I cannot afford to wait any longer. This has had a very negative effect on my credit status and score on the Credit Bureau and I need this letter so I can resolve that with the Credit Bureau.