You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I serve you?

USER: Could you please book a flight ticket from OAK to DEN?

ASSISTANT: Sure, may I know the travelling dates?

USER: My travelling dates are Dec 18 and Dec 20.

ASSISTANT: Do you have any connection limit?

USER: I need a single connecting flight.

ASSISTANT: Do you have any other requirements?

USER: No.

ASSISTANT: May I know your name?

USER: I am Virginia Thomas.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: Sorry, no flights found with your chosen dates.

USER: No problem, thank you.

ASSISTANT: Thank you for opting us.