This is an "IRS" scam. The IRS would send you a letter not just a phone call about a law suit being filed against you. They have sent me letters when there was something they wanted proof about.
Not a phone call.
Said there was a lawsuit against me for $3,000.00 from 2012-2016. Gave me his name, badge number, case numbe and a warrant number. I told them they was a scammer and he said when we hang up the phone cops will be at my door in about 45 minutes. From 2010-2016 we used H.N.R block. They knew my name and my address. What worries me if they know that information on me what else do they know.