Some solve that with an answering machine - leave a message and set up a time for a call. Pretty much the same method we used back in the old days to call a fri

Some solve that with an answering machine - leave a message and set up a time for a call. Pretty much the same method we used back in the old days to call a friend "Hi Mrs Johnson, is billy there? No, he's out. Ok tell him I'll call back at 7pm" Telephones don't need to be real-time.