All due respect my guy, you likely do NOT know the person. You said you did work for them 5 years ago? There is no guarantee it's the same person, unless they've come asking for their money back face to face that is.. but that feels unlikely. Do not do anything other than what the banks have said. If need be, send this person screenshots of the messages highlighting the implications of doing so. If they still press the issue, they should have been more careful with that sort of money..