Don't be *******, bring my money back!

Last month Capitec Bank debited R250 more than they should have on a loan repayment so I assumed that this month they would let me pay R500 of the R750 monthly repayment of the loan. But instead the lady I spoke to on the phone told me that she wasn't sure if Capitec would actually do that and when I look at my amount payable status it says I should pay R750 again this month even though they already took the R250 last month so what I want to know is this, if Capitec is not going to credit me then what are they going to do with the extra money they too from me last month?

I also need Capitec to know this, personally I would like to never have anything to do with this bank ever again and being blacklisted is not an issue for me because I'll just stop paying the loan and continue to live in this hole I am living in right now. I've been doing my part and paying back the loan as best as I can without any arrears but this bank is now taking it too far by trying to ***** from me