You can go to your cell service provider's web site, and they should have a blocking program. Verizion does, anyway. I just log into my Verizon account and enter the number I want to block. Anyone calling after they have been blocked gets a message to the effect that "the number you have called is not accepting calls at this time..." This number just got blocked! ;-)
Got a call from this number. Answered to absolute silence. Ironically 2.5 hours earlier got a call from 213-337-2559 from Los Angeles, CA. Didn't answer and they left no vm. Makes me think it is coming from one central # just disguising it somehow. Seems very scamish & dangerous to me to attempt to answer these calls. I won't answer these calls again and will block them.