You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Raymond Walker. Can you change my previous reservation?

ASSISTANT: Sure, I will help you out. Ok, please wait a moment.

USER: Ok.

ASSISTANT: Sorry, there are no reservations found. Thank you for approaching us.

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