You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I am Betty Walker want to visit IAD, can you book a ticket from OAK?

ASSISTANT: May I know your desired travel dates please?

USER: Sure, my travelling dates will be 01/21 and 01/23.

ASSISTANT: Please wait a while.

USER: Ok.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: That's ok, thank you.

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