You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am planning to change an existing reservation, due to health issue. Can you please change my reservation?

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

USER: Thank you.

ASSISTANT: May I know your name please?

USER: I am Gary Hill.

ASSISTANT: Wait a moment please.

USER: Sure.

ASSISTANT: Gary Hill, we regret to inform you that there is no reservation found on your name in our records.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for choosing us.