Of course they don't want you to talk to anyone. They didn't want someone to stop you from paying them. These are foreign criminals. this is the most publicized scam in America.
IRS Scam:
The IRS does not need to sue anyone. They send you first class letters delivered by the Post Office. Several of them. Ignore those, and they then send certified letters that you need to sign for. Again delivered by the Post Office. Ignore those and they simply freeze your bank accounts and anything else you own. If they can do that, then why would they bother with a court case that might take them years before they get in front of a judge? They also do not bother arresting people for a few thousand dollars for the same reasons I have already given.
Official IRS Government site detailing this scam and providing links to report it:
http://www.irs.gov/uac/Newsroom/IRS-Warns-of-Pervasive-Telephone-Scam
https://www.irs.gov/uac/Online-Scams-that-Impersonate-the-IRS
https://www.irs.gov/uac/Tax-Scams-Consumer-Alerts
https://www.irs.gov/uac/Newsroom/Phone-Scams- ... 6-Filing-Season
https://www.irs.gov/uac/Newsroom/IRS-Complete ... -Scams-for-2015
Clearly a fishing scam. They called with an unintelligible company name "tax fraud department IRS" claiming that the IRS was going after me and unless I called them back, my case would be going to court. Don't fall for it.