Being handed over to the legal department, for apparent non payment

I rented a car with Europcar last year in August, asked to have a repayment arrangement with Gloria Van Zyl, and all was in order (well at least that's what I thought). A year later I am constantly being harassed by debt collectors, demanding payment of outstanding monies with interest. Now it's a back and forth between Gloria, the debt collectors, and I, to have this matter sorted out to no avail. The question is, to whom is all the money that I paid, allocated to, since I paid them up, yet I am being constantly harassed by their debt collectors to pay? I have been promised to have this matter sorted, and Gloria keeps making promises to resolve this matter, that she is clearly failing to keep, AT MY EXPENSE. This is utter poor and pathetic service, and would not recommend this company to anyone at all. After all this, I still await a resolution. How disappointing