Sending people to place of work without notification asking for personal information

Today I had 2 people come to see me at work in connection with my account that is 'overdue'. No appointment, no notification from African Bank which is fine, however these people want you to complete a document stating your banking details, ID number and residence. When I phoned the call center all they said was yes we have tracers. But didn't take it seriously when I told her I got no notifications. They are not from any legal firm so I am sure you are not allowed to be sharing my information with these people. In the world we live in, there have been many people pretending to be from other companies and ****** people. How can you allow this? In the end, they didn't allocate my payment correctly.