You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: Need your assistance for booking a flight ticket to Las Vegas with a direct flight.

ASSISTANT: Sure, may I know your planned travel dates?

USER: I would prefer to travel on the month of March and preferred dates are 01 and 03.

ASSISTANT: May I know your nearest airport codes please?

USER: Sure, airport codes are from ORD to LAS.

ASSISTANT: Do you have any time preference in departure and arrival on your journey?

USER: No.

ASSISTANT: Do you have any another preferences on this trip?

USER: No.

ASSISTANT: May I know your name for the booking process?

USER: Sure, please book my ticket on the name of Robert Anderson.

ASSISTANT: Sorry , no flights are available on your specified dates.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Welcome, thank you for reaching us.