IRS does not file lawsuits. They have enough administrative authority under the Tax Code and related regulations to collect all taxes lawfully owed to federal government.
They just called from this number and are stating that the IRS is filing a lawsuit against you and you need to call them back at the number. Do not call. I repeat do not call!!! If the IRS is suing you or needs to get a hold of you they will mail you something and they do not give out their "direct line." They have a 800 number you call back not a direct line.
The IRS has a processing center where mailed-in returns are handled, and they have a walk-in office (appointment times have to be made) in a strip mall at the Rundberg intersection with Interstate 35. They might have another office elsewhere in Austin, but I have not looked for it. In 2010 the IRS had an office on Research Boulevard (US Highway 183) and Joe Stack flew his airplane into that building. https://en.wikipedia.org/wiki/2010_Austin_suicide_attack
Congressional hearing:
http://www.nbcnews.com/business/taxes/tax-imp ... hearing-n341906
Canadian tax payers should click on the "Canadian_Info" link, below:
Canadian_InfoSeveral links, describing Canadian tax scams: