Folks - we have all 5 area codes in the state of Washington BLOCKED.  So simple, so easy.
Approximately 2 years ago we bought a digi tone call blocker and the first numbers that went into it were all the area codes from Washington State.  What a life saver!
These scammers change phone numbers all the time to fool call blockers but if you block the entire area code, they can't get through!  
Our office phones do not ring (not even once) when a blocked call comes in and our office is not disturbed.
Please save your sanity and purchase a call blocking phone or device - preferably one that blocks entire area codes.  They're inexpensive and they work.
I understand that each area code has the potential of 10,000,000 phone numbers!  Amazing!
Currently, between our home and office numbers, we have nearly 95 area codes blocked along with several hundred phone numbers with area code.