Additionally another method used by the scammers are a computerized voicemail that claims to be the IRS and asks you to contact them. This is also a scam.
Feel free to hang up on these individuals and never give out sensitive information such as credit card numbers, social security numbers, or banking information over the phone unless you are positive you know who you are talking to is legitimate.
Lastly if the IRS does want to get a hold of you they will do it via the United States Postal Service.