Robocall with recorded message claiming to be the IRS (isn't that illegal too)

Return the call. The issue at hand is extremely time sensitive. My officer Julie Smith from Internal Revenue Service and the hotline to my division is 5853646540. I repeat it's 5853646540. Don't disregard this message and do return the call before we take any action against you. Goodbye and take care
 Jan 09th, 2015