This an Indian based IRS scam. Do not fall for this. read http://www.treasury.gov/tigta/press/press_tigta-2014-03.htm
Also report it to your local law enforcment agency. The scammers use magicjack (YCom corporation) voice over IP lines. This is against their terms of use and can lead to termination. However law enforcement has to initiate the contact with Ymax. If you are really annoyed: Call or write to your representative in Congress. As these scams are ongoing all over the country, maybe this will trigger a reaction....

Guys! I won $2.5 million and a new Mercedes! But to verify delivery I needed to call: 202-239-8723, which of course had a cacophony of dogs barking and a woman with a heavy accent. They're changing up their game, so be aware! The scam has changed but theyre still trying to scam people.

This number called said he was Mike Goodman from publisher clearing house. He had a heavy carribean ascent
Publisher clearing house never calls the winners so beware.