I switched over to VoIP service about 5 years ago.... best thing ever. I can block anon calls, invalid North America CID (all zero's or all one's), I can block by CID name, partial numbers, or individual numbers. Not only can I block, but I can select how it is blocked (busy signal, blocked call message, stop calling message) or forward the calls (rejection hotline, back to themselves, etc.).
I can also schedule times for a "white list", where a prescribed list of numbers will ring, all others go to voicemail.
That is pretty neat. Eventually I want to setup a voip server and do similar things at my house.