Their mistake is now costing me and they don't care

I have struggling to make my payments and I would get those threating calls and letters and rightfully so because I owed them. I couldn't make payments for two months or so and that affected credit record badly. I then decided to call them to request a settlement amount, and used all my bonus to settle the account amounting to R7 251.93. Now a month later I receive account statement with an outstanding of R1 794.48. After numerous calls made to them, I was told there was a mistake made by their consultant who sent me an incorrect settlement amount, therefore i will have to make more payment. I explained to them that reason I wanted to settle its because I knew that my budget will be tight in the next months and i won't be able to make it. Meaning their consultant mistake is costing me, Game account was no longer on my budget and I was told sorry there's nothing they can do from their side. To my surprise this morning I just received an email with a settlement of R1 819.42 i need to make within 5days.