You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I assist you?

USER: I am David Thompson. Can you please book a flight ticket to Washington, DCA frm Las Vegas, LAS?

ASSISTANT: Sure, Please help me with your travel dates.

USER: My journey dates are from 08/16 to 08/18.

ASSISTANT: Please wait a second.

USER: Sure.

ASSISTANT: Sorry, No flights found with your chosen dates.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you.