Pro-tip, perform mutual authentication: "Can you give a reference number (they will have a case number), and tell me where I can find your department's number

Pro-tip, perform mutual authentication: "Can you give a reference number (they will have a case number), and tell me where I can find your department's number on your website please. [Edit] I will call you back." I've never had a bank or other financial institution have a problem with this approach. I don't give myself the opportunity to be fooled, because all of us can be fooled, it's how I respond to every single call from a business.