Two of my friends with area code 831 can't call me

Two of my friends in area code 831 can’t make calls to me in San Diego. They are not on my block list unless community block list has generic 8xx area code. Even *82 doesn’t work. Why can I get calls from anywhere in US? They get "disconnected number "message as I set up for blocking community and personal block list. I reset for community block list to go to my voice mail but I don’t even want voice message from true community block listed numbers.

Who was your previous phone provider?
Are your friends using that same phone provider?
If they are, have them call their provider and complain that they can’t reach a known working number.
Actually they should call in any case since their provider has their forwarding tables configured incorrectly.

This can happen when a number is ported away from a provider and they mark the number as out of service instead of completely deleting it from their records. It happened to me when I left Vonage.