last week, i received three calls in one day  from this california number that is unlisted...there is never a message left, and when i try to return the call, nothing happens...no ringing, no voicemail, just a dead line. the next day i received two calls from the same number, with the same results. i do NOT answer calls from numbers i don't recognize, especially out of state (i don't know ANYONE in california AT ALL) and my cell phone number is listed in the Do Not Call register.