I got calls from this number but never a message.

This is a scam call pretending to be the IRS and say they are filling a lawsuit against you. If the real IRS was trying to get ahold of you it wouldn't be through a foreign contact center. They are trying to get information. I suggest either hanging up or giving them fake info just to waste their time. I called back and it sounded like a busy airport with others in the background asking for peoples info, that isn't how the real IRS operates. You would already know if the IRS is filing a lawsuit against you, phone calls wouldn't be the first notice.