Old Ma Bell phone service either doesn't have selective call blocking or it's so cumbersome to use or has so many limitations that it's really useless.
Change your land-line phone to a VOIP line - uses the Internet instead of old Ma Bell. There are MANY VOIP providers out there - be sure to find out if they have SELECTIVE CALL BLOCKING. Vonage STILL doesn't have it the last time I looked, but phone.com does. Google voip reviews.
Then set up your VOIP account so it only rings through to your phone for phone numbers you know - everyone else goes to voice mail. Of the few who bother to leave a voice mail you can choose to block future calls all together so they can't even leave voice mail again.