Unpaid debit order bank fee

Discovery Invest submitted a debit order to debit the Discovery Life payback that was paid into my account without my permission. Now Discovery has sent a form to change the payback option as all of this came about due to opening and linking a both policies. As I do not keep funds in my cheque account; the debit order failed and FNB has charged me R114. Please could this be reversed. R114 is a very steep amount which I cannot afford for an error that is not my own. Claiming back the bank charges from Discovery will be an added mission