You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Due to postpone of my exams, I want to change my existing reservation.

ASSISTANT: Sure, can you share your name for checking?

USER: Sure, I am Timothy Wright.

ASSISTANT: Give me a minute.

USER: Sure.

ASSISTANT: We have found your reservation, can you share your trip dates?

USER: Ok, my travelling dates are Mar 11 and Mar 13.

ASSISTANT: May I know your journey airport codes?

USER: My source airport code is PHX and destination airport code is LAS.

ASSISTANT: Do you have any preferences?

USER: I would like to travel in single connected flight.

ASSISTANT: There is a direct flight with number 1019  in airline Hawaiian, the fare is 100 in economy class. Can I book it?

USER: Yes, please confirm.

ASSISTANT: Your ticket is reserved, the depart time is 13:00 and return time is 6:00.

USER: Thank you.

ASSISTANT: Thank you for choosing us.