You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I help you?

USER: I am James Young. I am planning to book a flight ticket from CA - OAK to DC - DCA, could you help me in booking a flight ticket?

ASSISTANT: Sure, Please help me with your travel dates.

USER: I want to fly on 10/21 and return on 10/23.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: Sorry, No flights found with your preferable dates.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for opting us.