Double instalment payment

I took out a car finance plan with MFC and my first car instalment was due on 1 September.I dutifully phoned MFC and asked if I need to make the eft for my first car instalment or if it will be on debit order from my account. They told me that there is no debit order set up and that I must make the payment, which I dutifully did on 1 September. Then when I checked my bank account on 2 Sept, I see an automatic debit order did come off. MFC have said they will transfer the payment I made back to me within 10 working days. Clearly the MFC personnel (who told me that there was not a debit order set up) does not know what they are doing. I am shocked. This is a large amount of money that they owe me.