Who calls me from this number.  I called it back and it had a non working number message

1)   you are not obligated to talk to anyone on unknown phone numbers   2)  if it's important enough your unknown caller should leave a message    3)  if caller is rude or pushy just say "hang on a minute", put the phone down, and later, hang up when you the dial tone.   TIME is the most valuable asset to sales folks so the longer you keep them on line the more likely you will be removed from the call list.   It works for me !!