You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I have a plan for the trip, so please help me to book a flight ticket from DEN to DCA.

ASSISTANT: Sure, I can help you with that. Can you please help me with your travelling dates?

USER: Sure, the travelling dates are 07/19 and 07/21.

ASSISTANT: May I know your name to proceed further?

USER: My name is Ryan Thompson.

ASSISTANT: Thank you for providing. Ryan, I am  sorry to inform you that there is no flight available at your requested dates.

USER: It's ok. Thank you for your service.

ASSISTANT: You are welcome. Thank you for contacting us.