I've never received one of these calls, but someone should set up a VM and let them in. See what they do exactly, and then report it. If you could get enough in

I've never received one of these calls, but someone should set up a VM and let them in. See what they do exactly, and then report it. If you could get enough info on them, am sure the central office could be taken down very quickly, and the owners arrested. Just a thought anyway, exposing them is an excellent first step though, and am sure keeping them on the line is slowing them down a little.