INCOSISTENT AMOUNTS

I took out a loan with Capfin and the 25th of this month which happens to be on a week day was supposed to be my last payment towards the loan then my loan would be settled, on the 27th of August I was contacted by 1 of the consultants to inform me that my balance payable on the 25 of SEPTEMBER will be R1884.53 then I will have to pay a monthly fee of NO MORE than r100 on top of that, but this morning on the 23rd of September CAPFIN debited my account luckily for them, I had money in my account but I ddnt understand why they would debit on the 23rd instead on the 25th which is the agreed upon debit date, and if I had gone now to reverse that money they would still charge me yet they debited on a wrong date, but nonetheless, I contacted them to find out because they only debited R1574.11 instead of the r1884.53 which was agreed upon, now I was told no I must go and make a payment of R614.19, now if I calculate correctly, R1574.11 + R641.19 does not make R1884.53 now im told about interest and that my monthly fee was probably above the promised r100. How does this come to be when you have it on record? cz I asked about the interest and ws told no R1884.53 is all I have to pay + +-100