I've been getting those calls since May. They leave threatening voice mails about arrest warrants, bring my attorney and money or else. I googled and found that the IRS and FTC now have online reporting pages. They are serious about stopping these guys. Here is the link to the latest article and the reporting info is all the way to the bottom of the page. You can report online or call it in. I reported the last call to both the IRS and FTC as the page suggested. Just copy and paste the link into your browser if it isn't clickable or you can google IRS scam and click the link with irs.gov. Don't click on a .com link because it won't actually be the government website if you do.
https://www.irs.gov/uac/irs-warns-ta...nes-gift-cards