You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, May I know your good name?

USER: Sure, Richard Wilson here.

ASSISTANT: How can I support you today?

USER: I want to change my existing reservation, due to postpone of my exam. So, Can you please help me to change  my reservation?

ASSISTANT: Sure, we are here to help you for changing.

USER: Thank you.

ASSISTANT: Please give me a minute, I will check with the reservation on your name and revert to you.

USER: Sure.

ASSISTANT: Thank you for waiting, we did not find any reservation on your name to change it.

USER: No problem, thanks for your help.

ASSISTANT: Thank you for choosing us.