You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you?

USER: Please help me to book a flight ticket from DCA to LAS.

ASSISTANT: Sure, may I know your travel dates?

USER: My trip dates are from Sept, 28 to Sept, 30.

ASSISTANT: Do you have any connection limit?

USER: I need a single connecting flight.

ASSISTANT: Any other specifications to be met?

USER: No.

ASSISTANT: May I know your name?

USER: Shirley Clark.

ASSISTANT: Sorry, there were no flights found on your route.

USER: Thank you for your information.

ASSISTANT: Thank you.