They will eventually run out of area codes to call from. Don't bother blocking individual numbers, each area code can have millions of combinations. Just block the entire thing. Then they will have to start using area codes that are heavily used (like 214).
Someone pointed out that these are legitimate area codes. Yes they are but I don't know anyone that lives in these areas (and likely you don't either). If someone needed to get a hold of me they would know how to do it. In a worse case situation you could always just force them to voice-mail, if they had anything important to say they can leave a message.
Honestly, 99% of the communication I do is through texting .. which I find interesting they haven't started to spam us with texts.. perhaps its leaves a bit more of a paper trail.