You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Brian Barker.

ASSISTANT: How may I assist you?

USER: I am planning to travel from OAK to DCA, can you help in booking a flight for me?

ASSISTANT: May I know your travelling dates please?

USER: My travelling dates are 07/28 to 07/30.

ASSISTANT: Ok, please allow me to check with available flights.

USER: Sure.

ASSISTANT: Thank you for waiting and sorry for my late response.

USER: It's ok.

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

USER: That's ok, thank you for your help.

ASSISTANT: Thank you for reaching us, have a nice day.