Unreasonable in settling outstanding debts

I was retrenched at the beginning of last year but used part of my retrenchment package to continue my medical cover hoping that I would get another job before long. Unfortunately, my luck and money ran out and I had to cancel my medical aid at end September last year. Discovery then suddenly said I still owed them an amount of R8060, which I did not agree with, but decided to pay to maintain a good relationship for when I could afford to rejoin the scheme. I filled in their form and offered R500 a month, which they declined and demanded I repay within six months. They stated that I needed to provide all kinds of information and it would then need management approval. If I am earning half of what I used to earn how do they expect me to meet this demand? I cannot even afford the R500 per month, but will try to make some plan.They subsequently handed me over without further ado, when I advised them that filling in forms does not improve their chances of getting the money within six months. I have been bul**** and my name has now been blackened.