I just had an experience similar to the ones already posted:  a female called my mother's home phone saying she needed to verify my identity.  Within an hour, a male called and said I was being subpoenaed and he needed to speak with me ASAP.  I called and was floored by the unprofessionalism and threatening tone, included that it was urgent because a subpoena was going to be served at my workplace today, and he had the last 4 digits of my SSN.  He also offered to transfer my "debt" to one of my credit cards.  When I expressed confusion and disgust, including that I don't have any credit cards, he argued that they've investigated me and they know I do, and started rattling off numbers.  We then got disconnected.  He tried calling back twice and left one voicemail.  This must be stopped!!