You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I would like to change my existing reservation, due to examination schedule postponed. Can you please help me?

ASSISTANT: Sure, I am glad to help you out.

USER: Thank you.

ASSISTANT: May I know your name to check your previous reservation status?

USER: My name is David King.

ASSISTANT: Ok, please give me a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found on your name in our records.

USER: No problem, thank you for checking.

ASSISTANT: Thank you for reaching us.