You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: Can you help me to book a flight ticket from SFO to LAS?

ASSISTANT: Sure, may I know your name please?

USER: I am Stephen Lee.

ASSISTANT: May I know on which dates you are willing to travel?

USER: My travel dates are Apr 21 and Apr 23.

ASSISTANT: May I know your class preference please?

USER: I am comfortable with any class.

ASSISTANT: May I know your connection limit please?

USER: I prefer direct flight for this trip.

ASSISTANT: May I know your preferable time for journey?

USER: I am comfortable with any timings.

ASSISTANT: Sorry Lee, there is no flight found as per your travelling details.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.