I can understand why a Provider wants the Hobbyist to call; namely she can verify that an appointment is about to happen, get herself ready, etc...
Unfortunately, it's also problematic for the Hobbyist if he does not have a hobby phone. In today's age of technology all calls and text messages are available to a suspicious spouse, girlfriend or attorney.
It almost makes a call from a payphone the safest bet unless you want to stash a disposable phone in your pants.
Ladies, how about it? Can we just call you from a convenience store to confirm we're on our way and get final directions?