You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I want to book a flight ticket from SFO to DEN. Could you help me?

ASSISTANT: May I know your desired travel dates please?

USER: My travelling dates are from Jan 18 -20.

ASSISTANT: Do you have any specifications?

USER: I prefer for economy class with single connection.

ASSISTANT: May I know your name please?

USER: Jerry Mitchell here.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: That's ok, no problem.

ASSISTANT: Thank you for opting us.

USER: Thank you.