Omg I got the same email and what was funny was they said my SSN will be on hold and that I should explain to my employer and my HR what I have done lmao this [***] hole has nothing better to do LAME get a life!!
They are scammers and attempting to scare people into paying a bogus debt, a debt that's already been paid, or even a debt that is owed - but not to the caller. If you had committed fraud, you wouldn't hear about it via a scammy phone call or email - you'd have cops around at your door to talk to you and/or arrest you. Block these losers or ignore the calls.