Banking problems

I need some advice , instead of the father of my daughter being debited for her child support ... a perfect stranger had money taken out of his account .. I only noticed it was the wrong person after my bank phoned asking mysterious questions as to who set up the direct debit .. then I checked on-line ... They are not making it easy for me to give the guy his money back ... nor in fact trying to reassure me ... they seem to take no responsibility for the mess .. its been three days of me phoning them to try to get to the bottom of it . The documentation which my daughters dad set up shows all was in order .. so its a mistake further up the process ! Does anyone know if a banking ombudsman exists in France ... customer relations don't seem to exists .. I have no reassurance from the bank they will resolve the situation .. in fact they imply it is my problem to resolve .. which seems at present impossible as I have no idea who the person is that has been debited and whose money is languishing in my account ! Help !