There was one that worked up until a few years ago that was in the middle of the Mojave somewhere. Decades ago someone posted the phone number somewhere online, and people started calling it all the time just to see if anyone answered. They finally decommissioned it not too long ago

https://open.spotify.com/episode/5OoK9OTZ35SGJi18RSeR1i

E: this episode is from 10 years ago so I guess its been longer than I thought