Phone Calls About IRS Filing a Lawsuit?

Yes, it's a known scam. See, for example,

--Begin quoted text An aggressive and sophisticated phone scam targeting taxpayers, including recent immigrants, has been making the rounds throughout the country. Callers claim to be employees of the IRS, but are not. These con artists can sound convincing when they call. They use fake names and bogus IRS identification badge numbers. They may know a lot about their targets, and they usually alter the caller ID to make it look like the IRS is calling.

Victims are told they owe money to the IRS and it must be paid promptly through a pre-loaded debit card or wire transfer. If the victim refuses to cooperate, they are then threatened with arrest, deportation or suspension of a business or driver's license. In many cases, the caller becomes hostile and insulting.

Or, victims may be told they have a refund due to try to trick them into sharing private information.

If the phone isn't answered, the scammers often leave an "urgent" callback request.

Note that the IRS will never: 1) call to demand immediate payment, nor will the agency call about taxes owed without first having mailed you a bill; 2) demand that you pay taxes without giving you the opportunity to question or appeal the amount they say you owe; 3) require you to use a specific payment method for your taxes, such as a prepaid debit card; 4) ask for credit or debit card numbers over the phone; or 5) threaten to bring in local police or other law-enforcement groups to have you arrested for not paying.

--End quoted text

They also recommend contacting TIGTA at and the FTC at using "IRS Telephone Scam" in the notes

I hope you didn't provide them with any information.

It is a longstanding scam that many people are exposed to. If you are concerned, I suggest you start by Googling 'IRS lawsuit scam' and then read the the notices on the IRS website (e.g.: "IRS Reiterates Warning of Pervasive Telephone Scam").