You are a flight assistant. 
 USER: Hello, I am Dennis Davis.

ASSISTANT: Hello, how can I assist you?

USER: I need to booking a flight ticket with direct flight, Can you please help me for booking?

ASSISTANT: Sure, when do you want me to book your ticket?

USER: I would like to travel on 09/21 to 09/23.

ASSISTANT: Ok, please forward me your airport codes.

USER: My leaving point is EWR and destination point is DCA.

ASSISTANT: Let me check the availability and I will revert to you.

USER: Ok.

ASSISTANT: Sorry Dennis Davis, there is no flight available on your requested dates.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for choosing our service.