You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

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

ASSISTANT: Sure, may I know your planned trip dates?

USER: My travelling dates are Dec 5 to Dec 7.

ASSISTANT: Do you need any connection limit?

USER: I need a flight with single connection.

ASSISTANT: Can I know your name for documentation?

USER: My name is Helen Mitchell.

ASSISTANT: We are sorry to inform you that there is no flights are running on your route according to your given dates.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for approaching us.