You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I guide you today?

USER: I am Debra Williams want to shoot my film at Oakland, can you book a ticket with price under 200?

ASSISTANT: I will help you with that, can you please tell me your preferable journey dates?

USER: Sure, my travelling dates will be 04/11 and 04/13.

ASSISTANT: May I know your airport codes to proceed further?

USER: Yes, I want to fly from DCA To OAK.

ASSISTANT: Wait a minute.

USER: Ok.

ASSISTANT: I am sorry to say that there is no flight found.

USER: That's ok, thank you.

ASSISTANT: Thank you for reaching us.