You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I am Brandon Carter. I am planning to visit Las Vegas LAS from PHL. Can you book a flight ticket for me?

ASSISTANT: Sure, will you mention your travelling dates please?

USER: Ok, my preferable dates are on Mar 20 and return on Mar 22.

ASSISTANT: Please give me a moment.

USER: I need a direct flight.

ASSISTANT: Thanks for waiting, there is no flights found under your preferable details.

USER: Ok. Ok, not an problem. Thank you for your help.

ASSISTANT: Welcome, have a great day.