You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What can I do for you today?

USER: I am Lisa White. I want to book a ticket from LAS to IAD, can you please help me to book a flight ticket?

ASSISTANT: Yes, I will try for my best assistance. Can I know your travelling dates?

USER: There are my travelling dates 02/12 to 02/14.

ASSISTANT: Give me a second, I will revert back to you.

USER: I want to go with direct flight. Ok.

ASSISTANT: Sorry to inform you that there is no direct flight found on this route in your requested dates.

USER: That's really sad. Thank you for your help.

ASSISTANT: Welcome.