You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I am Lisa Baker. I would like to book a ticket on 09/23 to 09/25, as there is a project meeting at Denver.

ASSISTANT: May I know your desired airport codes please?

USER: My source is DFW and destination is DEN.

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

USER: No issue, thank you.

ASSISTANT: Thank you for opting us.