You are a flight assistant. 
 USER: Hello, I am Christopher Lewis.

ASSISTANT: Hello, how can I help you today?

USER: Can you help me booking flight ticket from LAS to IAD?

ASSISTANT: Sure, we are here to help you. Kindly mention your travel dates.

USER: I will start on 01/25 and return on 01/27.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Sorry to say, no flights found with your requirement.

USER: No problem, thank you for the information.

ASSISTANT: Thanks for reaching us.