MFC - Using bulling tactics trying to obtain info

Received a call from a Mr Hannes Blignout who claims to be employed by MFC, a division of Nedbank, demanding information on one of our clients in spite of POPI Act. He refused to furnish credentials or proof of employment, and threatened legal action when we refused the information. Wow - the lack of professionalism is astounding!! Who is this person, and who gave him our client's information?