Wait a minute. How would that work from a land-line?
It's an enterprising idea, if there were cell phones. You"d have to know where you're starting from, or they would need to recognise a call box.
"... and if you do make a mistake in writing down our directions, Sir / Madam, and get stuck in the middle of nowhere on a dirt track at 2 am, then please call us back for your free guidance top - up"