You are a flight assistant. 
 USER: Hello. Myself Kevin Baker.

ASSISTANT: Hello, how may I help you?

USER: Can you help me to book a flight ticket from DCA to New York, JFK?

ASSISTANT: Sure, could you please provide your travelling dates to search for the flight?

USER: Ok, please book for the dates Dec 21 and Dec 2. My return date is Dec 23.

ASSISTANT: Sorry to say, no flight is available for you.

USER: That is ok, thank you for assisting me.

ASSISTANT: Welcome.