Can never get it right!!!

I have had so many complaints from October 2014, and I just have had enough. I had 2 separate accounts which I then merged into one account with extra view in Oct 2014 which should have costed me R739.00pm. I was charged to my horror, R1654.00 the one month and they cant tell me how they got to that figure either. I stopped that debit order and payed the correct amount. Then the charged me R2089 the next month. Then they had to credit the other amounts which took them 3 months to do. Every month I have the same argument about the \credits"that need to be passed"