You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, may I know your name please?

USER: Yes, myself Sandra Taylor.

ASSISTANT: How can I help you?

USER: I want to book a flight ticket from DEN to DCA.

ASSISTANT: May I know your travelling dates please?

USER: I want travel in the dates of 12/10 and 12/12.

ASSISTANT: Sorry Sandra, there are no flights available regarding your journey.

USER: Ok, thank you for your information.

ASSISTANT: Thank you and have a nice day.