You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How could I serve you today?

USER: Can you please book a flight ticket from DCA to DEN?

ASSISTANT: Sure, to book a ticket may I know your planned trip dates?

USER: Thank you. I have planned my travel dates as Oct 18 and Oct 20.

ASSISTANT: Do you need any other requirements?

USER: I would prefer single connecting flight so please check with that.

ASSISTANT: Can I know your good name please?

USER: Sure, myself Kevin Clark.

ASSISTANT: Please give me a moment.

USER: Sure, take your time.

ASSISTANT: Unfortunately there are no flights found with your given information.

USER: Oh! It is sad to hear. Anyway, thank you for your time.

ASSISTANT: Thank you for choosing us.

USER: Most welcome.