**** to get more money from me

On the 26th August i settled a loan i was owing paid R34548.00 more or less that is after the debit order of R1801 went off on the 25th successfully. On the 25th September i get debited i went to reverse it at my bank, 25th October again the do same thing. Then i go to the branch i reverse again and go to African bank and ask what the problem is. I am then told that the settlement amount was incorrect i short paid with with R100 or something however now they expect me to pay R890. Which i refuse why don't i pay only the remaining that short? No one bothered to call me after the 34000 was paid to ask if i was settling so that they tell me i short paid. I refuse to pay the R890 i can only pay what was short i have had enough of this bank too quick to debit and over charge people.