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

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

USER: Yes, Please help me in booking a flight ticket from DCA to OAK.

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

USER: Ok, 09/06 and 09/08 are my departure and arrival dates.

ASSISTANT: Ok, please allow me a moment.

USER: OK.

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

USER: Ok, no problem. Thanks for the response.

ASSISTANT: You are welcome, have a great day.