You've helped me by deterring my studies

I went into your Sandton branch on the 23rd of December to inform them that, after almost a year of being unemployed and only affording the activation amount of R50, I would start a new job in January. I also informed them that my new job would not be paying me as much as I previously earned so I would then need to make a more affordable payment arrangement. The Consultant I spoke to and I then agreed on certain amounts as well as the date on which the debit order would go off. This, on my part, was a show of good faith. My salary is still getting paid into my FNB account and there was enough money available in my account the day on which the debit order was set to go off so there was no reason for the debit order to be unsuccessful. Because of your incompetence, however, you failed to play your part. Now, after I have worked my budget out based on the amount of money left over after my debit order dates, you have the audacity to not only debit my account on a day we did not agree upon, but you also want to penalize me for your mistake? I spent a good week hustling my behind off to get enough money for me to register to study AND still make it through the month. Thank you