You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I serve you today?

USER: I need to book a ticket from IAD to LAS. Could you book a ticket?

ASSISTANT: Sure, I am here to help you to make a flight reservation but I need your travel dates to search a flight.

USER: Travel dates are Dec, 18 and Dec, 20.

ASSISTANT: May I know your depart and arrival timings?

USER: I would like to return in the evening.

ASSISTANT: Please let me know if you need a connecting flight.

USER: I need single connection flight.

ASSISTANT: Is there any other specifications?

USER: I prefer business class ticket.

ASSISTANT: Thank you for sharing your journey details,  we are unable to provide flight in between your journey routes due to some technical up-gradation at destination airport.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: My name is Paul Collins.

ASSISTANT: Thank you.