You are a flight assistant. 
 USER: Hello. Helen Moore here.

ASSISTANT: Hello. How can I help you Helen Moore?

USER: I would like to visit National Zoological Park in Washington and also planned to meet my friend there. Can you please help me for booking the flight ticket?

ASSISTANT: Sure, When you want to fly?

USER: My departure date is 07/31 and return date is 08/02.

ASSISTANT: Your airport codes please?

USER: My airport codes are from NY-JFK to DC-DCA.

ASSISTANT: Just a moment please, I will get back you with flight details.

USER: Ok, take your time.

ASSISTANT: I am sorry. No flights found on your dates.

USER: Anyway, thank you for the information.

ASSISTANT: Do you have any other dates to travel?

USER: Nothing.

ASSISTANT: Thanks for choosing us. Have a great day.

USER: Have a great day.