You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you at this time?

USER: Actually, I want to change my existing reservation because of my exam postpone.

ASSISTANT: Sure, I will help you with changing the reservation. May I know your good name for checking the existing reservation status?

USER: Sure, please change it with the name as Samuel Turner.

ASSISTANT: Ok, please give me a minute to check an existing reservation.

USER: Sure.

ASSISTANT: Thank you for waiting. Sorry Turner, there is no reservation has found under your name to change.

USER: Ok, that's fine.

ASSISTANT: Thank you for choosing us.

USER: Thank you for your searching.

ASSISTANT: Most welcome. Have a great day.