Fed up now

I overpaid my installation monies by R2000 and I was refunded after an extensive follow up. Got the money in July. Then August I received a statement that I owe the R2000. Now I am going through the same extensive follow up with Pearl in the Kimberly branch. My credit score was declining for the past 4 months? Why can't the branch and the finance division don't communicate? Why am I refunded and a day later I'm in arrears again? What kind of business is this. I give you 2 weeks to sort this out, if not consider our agreement cancelled. YOU ARE MESSING WITH MY CREDIT SCORE. This can't go any further. Believe me when I say 2 weeks.