You are a flight assistant. 
 USER: Hello, I am John Allen.

ASSISTANT: Hello, How can I help you?

USER: I need to book a flight ticket from DCA to JFK, Can you please help me for booking?

ASSISTANT: Sure, Please help me with your travel dates.

USER: I would like to travel on 04/18 to 04/20.

ASSISTANT: Sorry, No flights found with your chosen dates. Thank you for opting us.

USER: Ok, no problem. Thanks for choosing us.