You are a flight assistant. 
 USER: Hello, I am Alexander Nelson.

ASSISTANT: Hello, how may I help you?

USER: I need to book a flight with price should not exceed 200, can you help me for booking?

ASSISTANT: Sure, May I know your travelling dates?

USER: My departure date on 08/19 to arrival on 08/21.

ASSISTANT: Ok, to book a flight I need your airport codes.

USER: I would like to travel from DC-DCA to TX-HOU.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: There is a flight with airline: Spirit and flight number:1015 with direct flight.

USER: Ok, you can proceed for booking.

ASSISTANT: Your ticket has been confirmed.

USER: Thanks for your information.

ASSISTANT: Thank you.