You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am planning to meet my colleague in Washington, so please book a flight ticket from OAK to DCA.

ASSISTANT: Sure, I am here to help you out. May I know your travelling dates please?

USER: I want to fly on Dec 03, return on Dec 05.

ASSISTANT: Can you please share your connection limit?

USER: I need a single connecting flight.

ASSISTANT: May I know your name please?

USER: My name is Donna Walker.

ASSISTANT: Do you have any other specifications?

USER: No.

ASSISTANT: Donna Walker, here are no flights available in your route with your preferences.

USER: No problem, thank you.

ASSISTANT: Thank you for choosing us.