[stuff4ben]

That's easy to solve, if they get confused when you ask for proof, just ask them for a number you can call them back on and the reason they're calling. However, it's easy enough to type, but harder to remember to do in practice though.

[SideburnsOfDoom]

Oh, I call them back on the number that I have in my address book. I just want them to never do it again. To anyone. It s a bad practice that serves only to condition users into giving out personal information to any random person calling up and pretending to be from a bank.