Unfairly listed for an amount that Discovery cannot explain to me

At 28 FEBRUARY 22, I owed Discovery R8 535.20, I then paid them: R2 000 on 6 March 22, and R2000 again on 23 April 22, and again I paid the last amount of R4000 on 15 Sep 22, I had a balance of R535.20 remaining, I then had to fight with them to pay hospital bills that they didnt pay for Feb 22, this resulted in them activating the membership again to pay for those medical aid bills that they failed to pay, when this happened, they paid me R4000 in error, which I immediatly paid back to them, they then told me that all of a sudden I am owing again and amount of R4 535.20, they cant explain to me where the additional R4000 comes from as my balance owing was R535.20, they notified that I owe R4 535.20 on 22 Sep 22, they didnt explain how this amount went from R535.20 to R4 535.20, which they are demanding, and have now gone and listed me on the credit bureau, first I had to fight with them to righfully pay out the claims they didnt want to pay to the hospital, after that long battle, they eventually paid the hospital, now all f a sudden I am liable for a R4000.00 that came out of nowhere that they cant explain to me where and howcome I now owe R4000 from a balance of R535.20, and have listed me without even explaining to me how they got to that amount that I owe R4 535.20, I dont want the person who called me for my previous hellopeter comments to call me again, she is junior and does not even know what is going on herself, I want a senior manager to call me to explain to me how it is that I all of a sudden owe another R4000, because you demanding that I pay this R4000 just like that, and when I dont pay it because I am not sure how I owe this amount, you list me on the credit bureau, its funny how companies have a right to list you but we as citizens have no right to justify why we have been unfairly listed