The most famous one in the UK was called FIST (Fantasy Ihteractive ?Stories? by Telephone or something) written by Steve Jackson (of Fighting Fantasy fame, not the American Steve Jackson)... premium rate telephone number got me into trouble more times than I can remember as a kid

I played them in and around the California Bay Area but I guess similar games were set up all over the US. They were free too. Every time I watch the movie Treasure Planet (2002) the narrator for the holographic bedtime story reminds me of the phone games.