You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello. How can I help you today?

USER: Please book a ticket from Philadelphia, PA-PHL to Atlanta, GA-ATL.

ASSISTANT: Sure, may I know your itinerary dates?

USER: My departure date is 12/27 and return is by 12/29.

ASSISTANT: Can I know your name to proceed further?

USER: I am Mary Harris.

ASSISTANT: Sorry Mary, no flight is available on your route.

USER: Thank you.

ASSISTANT: You are welcome.