You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

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

ASSISTANT: Sure, I will help you. May I know your planned travel dates please?

USER: My trip dates are from Sept, 15 to Sept, 17.

ASSISTANT: May I know your name please?

USER: I am Carol Allen.

ASSISTANT: Do you need a connecting flight?

USER: I need a direct flight.

ASSISTANT: Do you have any other specifications?

USER: I prefer an economy class to fly.

ASSISTANT: Please wait a moment.

USER: Ok.

ASSISTANT: Carol Allen, no flights has been found on your planned travel dates.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for choosing us.