Disregard any instructions left by in the messages, if you've received nothing in the mail, you're in no danger. Do not call back unknown numbers or any left in bogus messages. There's nothing real about this so don't worry, or pay any attention to it. Turn off any answering machine and ignore the calls, you won't hear from these fraudsters again and they can't leave threatening messages.
Report the Calls to the real IRS here:
•report the incident to the Treasury Inspector General for Tax Administration at 800-366-4484.
•You can also file a complaint with the Federal Trade Commission at FTC.gov. Add "IRS Telephone Scam" to the comments in your complaint.
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Do consider getting a call blocking device or phone.. You can google them and many are around $40.00 or so.If its a cell phone, some already have call blocking, if not, there are free apps on the web that will work for some. You can google this. If you have a smart phone, there is a free app called call control. Iphones appear to have apps also. Another one is called Mr. Number.
Never return the calls. If you return the call they might get the impression you are vulnerable in some sense and then they hammer you with even more calls. Simply ignore them and block their calls.