You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I be at your service today?

USER: I need your help to book a flight from IAD to PHL.

ASSISTANT: Sure, I will help you in booking the ticket. May I know your travelling dates please?

USER: Sure, I want to depart on May 22 and need to return on May 24.

ASSISTANT: Do you have any other specifications?

USER: I need a direct flight.

ASSISTANT: Please help me with your name for booking.

USER: I am Benjamin Lee.

ASSISTANT: I am sorry no flights found on your route.

USER: Ok, no problem.

ASSISTANT: Thank you for choosing us.

USER: Thank you for checking.