I think this is probably a collection agency. They called my work number asking for a person that hasn't worked for the company for over two years, demanded HR, refused to say who they were, they were very rude and spoke in a very harsh tone of voice. When I advised I was google'ing his number he told me, "Good luck with that!" and re-demanded HR. He called me a liar when I said I needed to know why he was calling (what he needed) to get him to the right place. He hung up on me when I referred him to the employment verification third party we use.