I got one saying it was the IRS and they were suing me and it's my final warning . Oddly enough I never received a letter or prior phone call . Even if it was the IRS H&R Block is paid to handle this . I did try calling and was a busy signal . Didn't call from the same number they called .
This has happened to me before. If the IRS wants money from you trust me they won't have a robot calling you on the phone. There will be a certified letter sent to your home with a bill.