You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: Myself Catherine Taylor. Could you please help me to book a flight ticket to DEN from DCA?

ASSISTANT: Yes, I will help you. Let me know your preferable dates?

USER: My trip dates are 07/24 to 07/26.

ASSISTANT: Thank you for your information. Sorry, there is no flight as per your dates. Sorry for inconvenience.

USER: Ok. No problem. Thank you.

ASSISTANT: Thank you for contacting us, have a nice day.