It's the IRS scam. Read here:
https://www.irs.gov/uac/newsroom/irs-repeats-warning-about-phone-scams
http://www.forbes.com/sites/johnwasik/2016/06 ... u/#6cb8a18e171f
https://www.pindropsecurity.com/irs-phone-scam-live-call_analysis/
http://money.cnn.com/2016/05/25/news/irs-impersonators-scam/
Report here:
https://www.treasury.gov/tigta/contact_report_scam.shtml