Both times OPM was hacked. The first one used my maiden name which I haven't used since the 1970s, big tip off there, then they threatened to contact and charge my sister using her maiden name and I had just passed a federal background check so I knew that they were full of it. The call came from a state I used to live in, or so the number indicated.
My sister did call me within hours and said she got a weird call about this alleged issue, I told her it was a scam.
The second was using a number that was one digit off from the county court clerk's office where I lived. Said I was being contacted about an alleged 'judgement' against me and that I had to call back on a 1-800 phone number with a reference number to use and that I had to respond right away to make payment arrangements.
Their big mistake was twofold, once again I had just had a federal background check weeks prior and knew that I was not in any legal trouble because the feds would have let me know about it and I happened to be at the county courthouse when they called. I told them I was unaware of such an issue and that I would just go into the courthouse and speak with the clerk about it to which they insisted I had to use their phone # and the reference #. I insisted that I was going to go in to talk to the clerk and ended the call after which I went right to the clerk's office from which the call allegedly originated, showed them the number on my phone and described what happened... they were pissed.
I blocked the number and that was that.
Nobody ever calls you about such matters, if anything, they will either contact you by mail or someone comes to deliver a summons or the like. No judgement is issued without your knowledge in 90% (?) of cases of this nature. And the IRS does not make calls to your phone either.
I was aware of the OPM hacks so I was anticipating some kind of mischief regarding my personal info.
Now that our PII is up for sale to any and all buyers, Best be super critical when receiving such scam calls.