Loan nightmare

I took out a loan of R1500 which I was supposed to pay in 6 months, I managed to pay it off in 2 months. However, despite me settling the R1100 before the 25th they still debited R412 instead of R385 that was remaining. I tried sending them an email and I got no response from them. Now they plan on debiting again this month. I am being **********.