debit order reversal

I'm doing a bookkeeping and pastel course through damelin correspondence. It is extremely expensive, as it would be at any college, but I want a better future so I'm willing to pay it. A month ago I paid all the money I still owe Damelin, it was in the beginning of September. I sent a proof of payment and was assured by the lady that she had received it. 3 Days ago I saw that the debit order for Damelin had gone off again. I called today and was told that I need to go into the bank and have the debit order reversed. I explained that the reason I'm doing correspondence studies is because I work from 7 to 5. they said that if they do the reverse then it will take 90 days. That is absolutely ridiculous. Because Damelin made a mistake, I have to take off work, I have to pay the banking fees, and I have to drive out all the petrol to a bank - I work out of town. Worst service ever Damelin.