Refund my money

There is a transaction on my bank statement that i was not aware of, it appear as a MFC debit order of R115, i contacted FNB to ask what the debit was for and they told me that it was for unsuccessful debit order ran by MFC, they say MFC attempted to deduct again which does not make sense to me because all debit orders notifies me whether successful or not . but this has never notified me to prove that its untrue. even if it was true the debit order would have gone through because i had just gotten paid. if there are insufficient funds my account would have been on minus. PLEASE refund my money