You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: Shirley Carter here. I want to visit Washington DC - DCA to meet my old friend. Please help me in booking a flight ticket.

ASSISTANT: Sure, may I know your depart airport code?

USER: My depart airport code is WA - SEA.

ASSISTANT: At what price range are you looking for?

USER: I can afford up to 500.

ASSISTANT: Please share me your planned travel dates?

USER: My travel dates are from 06/27 to 06/29.

ASSISTANT: Do you prefer economy or business class?

USER: I am comfortable with any class.

ASSISTANT: I am sorry to say that there is no flight on your details.

USER: No problem, thanks for your information.

ASSISTANT: Thank you so much for choosing us.