You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Can you please help me to book a flight from DCA to OAK?

ASSISTANT: Please provide your travelling dates.

USER: My travelling dates are Oct 16 to 18.

ASSISTANT: Is there connection preference?

USER: I prefer a connecting flight.

ASSISTANT: May I know your name?

USER: I am Elizabeth Johnson.

ASSISTANT: Sorry, there is no flight with your travelling dates.

USER: Thank you for checking.

ASSISTANT: Thank you.