Aug 29, 2016
That's because they have no idea who you are. They just have a computer dialing lists of numbers and they hope to get some poor, unsuspecting victim to believe them. It's a big SCAM. Just a bunch of thieves. Here's some info on them from the real IRS and a report of some of thieves who were caught.
https://www.irs.gov/uac/newsroom/irs-repeats-warning-about-phone-scams
http://money.cnn.com/2016/05/25/news/irs-impersonators-scam/