Charging interest unnecessary

I took a loan with capitec last year and it was a long term loan. I took 25 000 for 24 months term. I've been paying since from last year but the loan was not going down and in June the app was showing that I am left with 14 months to settle my loan. On the 26 July this year I called collections department requesting to reduce the term of this loan from 14 months to 5 months... Okay everything went well and was told that they will increase my monthly installment from R1423.80 to R3074. 84 and they will start debiting me on the 29 of August okay I agreed with that. On the 28 was debited R3074. 84 as per agreement but I'm not happy because capitec has increased my monthly instalment and the interest charge. Lastly I was paying less installment and the interest charge was 234 rand but now I'm paying high installment and the interest charge is 413 rand why so