收到 202－239－0041 電話

昨天收到一個很奇怪的電話， 說是IRS audit dept 打來的。
聽起來不象native English speaker. 電話接線也很差，因當時急於忙別的事，問了好多次到底要我幹什麽，
也沒說清出，說讓我和他的supervisor talk, then a similar 口音的人有和我講了一篇， 說我們的談話要錄音，
還是聽不懂他要幹嘛。 感覺I am in trouble. I told him I got go, will be back in 2 hour. 

I then called police, and told this is a scam.
In the later afternoon, this person called me again. I told him I called police and reported this case, then hang up the phone.

First time to receive such a call, got very nervious, wonder if this kind calls are very often recently?
How can I tell if a call is real or scam?

Thank you very much in advance