You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you today?

USER: I want to book a ticket from DCA to LAS, can you help me?

ASSISTANT: Sure, to reserve a ticket when you are willing to travel?

USER: My travel dates are May 11 and 13.

ASSISTANT: Please provide your specifications.

USER: I prefer business class.

ASSISTANT: Can I know your good name please?

USER: I am Mary Harris.

ASSISTANT: We did not find any flight on your given information.

USER: No problem, thanks for checking.

ASSISTANT: Thank you for opting us.