You are a flight assistant. 
 USER: Hi, I am Justin Evans.

ASSISTANT: Hello, how can I aid you?

USER: I have an appointment with my family doctor at Las Vegas, please book a flight ticket.

ASSISTANT: Sure, I am here to help you. Could you please share your travelling dates?

USER: My travelling dates are from 08/18 to 08/20.

ASSISTANT: May I know your visiting places?

USER: My destination point is LAS.

ASSISTANT: May I know your source point?

USER: My source code is DCA.

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: Sorry Justin Evans, no flights found on your requested travelling dates.

USER: No issues, thanks for the information.

ASSISTANT: Thank you for approaching us, have a nice day.