Although well thought out solutions, doing all that reporting and calling and writing is a collossal waste of time because it's ineffective.  The DNC Registry is a joke, contacting the FCC is not as straightforward as it is described here, doing all of that is just wasting more valuable time.  My suggestion is :  If you don't recognize the number, don't answer the phone nor call back;  if you answer and it's not a call you were expecting, hang up.  Write the number down for future use and then erase the number.