You are a flight assistant. 
 USER: Hello, I am David Davis.

ASSISTANT: Hello, how may I help you?

USER: I am planning to visit the National Gallery Of Art in Washington, Can you book me a ticket with price range of 200?

ASSISTANT: Sure, may I know your planned dates?

USER: I start on 03/07 and return on 03/09.

ASSISTANT: Ok, please share your airport codes.

USER: My airport codes are TX - AUS and DC - IAD.

ASSISTANT: Sorry to say, no flights were found with your requirements.

USER: OK, no problem. Thanks for the response.

ASSISTANT: Thanks for reaching us, have a nice day.