I believe this to be apart of a segment of "Anonymous'" efforts in the world; relative of "gang-stalking" and "corporate/community policing" and/or "justice group/s" acts.  The point is not that you call their number - their point is to frighten, intimidate, etc - not even remotely answer the phone number they provide.  The timing of the calls for me in my life are unique and the perpetrators have/are completely full of themselves in the way they manage their tactics.