You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, Good Evening. How may I guide you?

USER: I would like to book a ticket from LAS to DCA, can you help me in booking?

ASSISTANT: Sure, can I know your preferable dates?

USER: My travel dates are 12/18 and 12/20.

ASSISTANT: Please hold on for a moment.

USER: Ok.

ASSISTANT: Can I know your name?

USER: I am Jack Baker.

ASSISTANT: I am sorry to inform you that there are no flights available with your dates.

USER: No problem, thanks for checking.

ASSISTANT: Thank you, have a good day.