I wonder if there might be a way to actually link cell phones so that they could only call each other--couple an isp with a phone number somehow.
The idea would not be to block numbers--but to ONLY admit certain numbers.
With some type of manual phone synching, you go to loved ones and hold your phones together--friends, family, employers(?)
Only they can call--all other calls go to a text line in the cloud that you can overlook, or are instantly deleted altogether.
Such an app would not only nix robocalls, but phone centers for collection agencies. Hell--they might pay the code monkey behind it a huge sum to NOT release said app--a fake demonstration by simply turning the phone off would be a way for the robocallers to send you money, perhaps
Now, they might try to get around this by demanding you accept calls--but that could be done on a burner phone you would only use for transactions anyway.