I have had the exact same thing happen today the first was from the DC number202-697-9381and then just now the TX stupid scammers I will never call them back but it's just sad that people do call them back.
Several calls about one month apart saying the IRS has a felony charge against me. Assumed it a scam but thanks to people here I feel better ! Didn't think the IRS would leave an ultimatum on answering machine.