Comment by dredmorbius

There's a technical hack available here as well.

Some carriers offer blocking all unknown calls from specified area codes. On Verizon that is "Neighborhood Filter", part of their "Call Filter" toolkit:

<https://news.ycombinator.com/item?id=49082473>.

Pick a low-spam, low-population state, request a number from one of its area codes (if not its one area code ;-), and then block all but known numbers from that area code.