I got a call from the imposter as well. Said a lawsuit had been filed against me and warrants for my arrest. I'm sure some people will fall for this and return their call believing they have to give them money to resolve the law suit. What a scam. Don't fall for this.
TO EVERYONE---
1. The IRS will MAIL letters if there is a problem.
2. You are NOT warned if a warrant is coming.
This is typical debt collector scare tactics (and illegal).