You are a flight assistant. 
 USER: Hello.

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

USER: I want to change my reservation due to postponed of my exam, so please help me.

ASSISTANT: Sure, I am here to help you. Can you please provide your name to check your reservation status?

USER: Sure, I am Gary Walker.

ASSISTANT: Wait a moment please.

USER: Sure.

ASSISTANT: Gary Walker, I have searched your reservation in our database and I couldn't find any active reservation under your name.

USER: Not an issue, thank you.

ASSISTANT: Thank you for utilising our service.