Caller ID says "unavailable", which means I am unavailable, too, so they'll have to leave a message. Message says that the IRS has filed a lawsuit against me. If you get one of these, it's bogus. The IRS NEVER makes a first contact by phone or email. They ALWAYS use snail mail, or direct knock-on-door contact in certain situations.
Got a call 2 days in a row, with no message. I'm finding I am being bombed by out of state called from all over the country to my cell phone which I never give out. I'm reporting them all to the Do Not Call people.