Bad service Vodacom

I had a contract with Vodacom that expired in March 2020. Well in advance I went in and gave them notice that I did not want to continue with contract and change it to a pay as you go. Vodacom then changed it accordingly and the last amount due on the contract was collected by debit order on the 1st of March 2020. Recently as I was applying for a bond I noticed that I was listed on the Credit bureau for this same contract that has been changed to Pay as you Go. I was listed for not paying the last amount (that was actually collected by debit order on 01/03/2020) and also for being a non-payer for 6 months (Apr 2020 - Sept2020), although it changed to a Pay as you Go from 01 March 2020. Clearly Vodacom did change the contract but their record keeping seems to be non-existent. I managed to get a letter, after a month of forward and backwards getting them to change it on their records, however I just got a letter which states that this outstanding amount has been settled now. In other words it seems like I only paid the amount now, and the 6 month non payment will still affect my credit score and profile and jeopardize my bond application. And still impossible to get to speak to a senior person to get this rectified at the credit bureau and /or supply a letter in which they acknowledge that it was due to their mistake and negligence. Also during these 2 years not one notice or call in which I was informed that I "apparently" still owed them money as I would have then picked this issue up early enough and not now when I am in dire straits of getting a bond approved.