I was receiving calls from this number and about 30 others 10 - 15 times per day over a 30 day period. They say they are with a federal agency and I am either due money or I am being sued by the IRS. Some of the numbers I have called right back and they are "no longer in service" or I got a recording that all representatives are busy, leave my name and number for a call back, which I don't do.

Nobody worth talking to calls me on my landline. I have started answering the phone in a recording-like voice with: "The number you are calling from has been reported under the Tele-communications Fraud Act.  Please hold for the next available agent to answer questions regarding the nature of your business.  You are hereby advised that all calls are being recorded and traced."   I rarely get past the first sentence before the caller hangs up and I've never had anyone stay on after the last sentence.  The calls have decreased significantly in number and frequency to about 2 per day and always from numbers outside my local area code.