Blacklisted for the wrong reason

Jet Store account I had an account with Jet store for many years, over 10 years, but I had a very bad experience with them since 2023, on the 23 of February 2023,i went to Archive Store in Vaal Mall because I wanted to buy a pair of sneakers, so I paid up my Jet account there as I normally use my card there, I even paid extra because I wanted to make a purchase, my outstanding balance was R980 but I paid R1200 so that I can get enough credit, after I made a payment, I was told that it has not yet reflected, so I said I will come back after 30 minutes, after an hour I went back there and the story was still the same, I left and told myself that I will go the next day, on the next day I went to Jet store in Vaal Mall, I asked them to check for me, but they told me it showed an outstanding amount of R980 still, I asked them how they said they don't know, I had a receipt with me that showed I paid, I showed them that receipt but I was told that because it was on weekend, I will have to check during the week, during the week I went to Jet president Square Vanderbijlpark, but I was told to send an email to Blake and associate which I did on several occasions, but still, I was not assisted but rather got letters to pay that account or they will blacklist me, I even went as far as involving Law on call lawyers from FNB as I'm paying them but they failed to assist me also, Thea went on and on for the whole 2023 until this year I was still sending proof of Payment to their lawyers but nothing changed, on the 9th of September 2024,,i send a proof of Payment again to the new lawyers who were calling me about that account and they stopped calling me, I thought the matter was resolved, to my surprise, I app**** for my son at a particular school for Grade 8 next year, I was told they can't accept my son because I was blacklist /written off by Jet stores because I did not pay the account, so please assist me, I don't know what else to do now, but I feel drained about this matter now Hope you find the above in order and I will hear from you soon. Thank you