Gullible new staff

I had a new host working yesterday. I was there to coach and help her as it was her first shift alone. She came to me with the phone as I had a call. I said " I'm sorry you didn't know I don't take phonecalls on Tuesdays". She apologized and turned away - I stopped her before she could take a message.
I told ______ , if it doesn't sound logical, please question it. As a manager, I do make mistakes. Your staff should feel comfortable on questioning you on decisions at times. The explanation of why you do what you do can go a long way towards employee satisfaction, performance, positive work environment and overall guest satisfaction - happy employees=happy guests.