Debicheck orders go off on unauthorized dates.

Good day, Debicheck dates are approved for a certain date. Mine was for the last day of the month. This is the second month my debit order goes off whenever an amount gets paid into my account even if it is a reimbur*****t for something I bought and not a salary. I have disputed this last month and was charged R45 to reverse this. Now again this was done just to be told it can not be disputed. I signed and agreed for a specific date and if this is not adhered to, well then my money is not safe in your bank and I should perhaps change this. I expect this to be reimbursed plus my bank charges.