I got the voicemail also because I didn't know the number. Then I answered it and got an automated message saying 'The IRS is filing a lawsuit against me' and 'call now to get more information'. Total Scam!
Scam posing as the IRS..."message left stating" call this number the IRS is filing a law suit against you. To get more information about this file call this number: 213-618-1561