You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you today?

USER: This is Kathleen Hall, can you help me to book a flight ticket from DEN to LAX?

ASSISTANT: Sure, on which dates would you like me to book a flight ticket for you?

USER: My preferable journey dates are Dec 18 and Dec 20.

ASSISTANT: In which class would you like to travel?

USER: I am comfortable with any class.

ASSISTANT: Do you have any other requirements?

USER: I would like to return in the evening time.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, there were no flights found on your route.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for contacting us.