You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: Can you help me to book a flight ticket from DEN to SFO?

ASSISTANT: Sure, please share me your journey dates.

USER: My travel dates are Sept 30 and Oct 02.

ASSISTANT: For booking, we need your good name. Please mention it.

USER: I am Mary Turner.

ASSISTANT: Do you need direct flight or connecting flight?

USER: I need a flight with single connection.

ASSISTANT: May I know your class preferences?

USER: I prefer to travel in business class.

ASSISTANT:  We are unable to provide flight in between your journey routes due to some technical up-gradation at destination airport.

USER: Can you please help me to recheck that I would like to depart in evening time.

ASSISTANT: Sorry, no flights are available.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for opting us.