You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, do you need any help from us?

USER: I am Barbara Davis. Can you please book a flight ticket from JFK to DCA?

ASSISTANT: Sure, could you please share your departure and arrival day?

USER: Sure, I need to travel on dates of 07/26 and 07/28.

ASSISTANT: Ok, please allow me a moment.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no flight on your requested travelling dates.

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

ASSISTANT: You are welcome, have a great day.