Give me my refund!!!

MFC deducted a debit order, even though I paid them a week before via EFT. I did not give permission for this additional debit order either. Now they owe me R1434.53. I have sent them my info and asked for a refund immediately as this is money that I need to survive on. The only reply I got was that they received my email. This was on Monday, it's Wednesday now. Still nothing.... How can you take money out of my account without my permission, PLUS ITS MONEY THAT I DO NOT OWE!