Double debit which bank refuses to repay

Dear Steve. Last month there was a mistake (on my part) where I transferred an incorrect amount out of my company cheque account which resulted in my debit order for my c/c to bounce. (This actually should have been the basis of another complaint, because I tried to rectify it immediately, but both card division and banking couldn't tell me what to do - both said I should ask the other one). This month I have been double debited for the amount. I complained and was told its correct. I complained again, and they sent me a reconcialliation which blatantly shows a double debit for R8100.10. I keep track of my accounts, its clear when I have lost R8100. They will not explain to me where the double debit comes from, in fact they always just give me the same answer, it's all correct, balance brought forward blah blah. The bottom line is that they have ****** R8100.10 from me, which has a serious impact on my business. I will be instituting legal action for the interest plus damages. I also want to state that I have been a reasonably happy customer for more than 25 years.I will be closing my company account, personal account, my platinum c/c and my wifes account and c/c's and moving on.