You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Could you please change my existing reservation?

ASSISTANT: Sure, can I know your name please?

USER: Yes, my name is Raymond Anderson.

ASSISTANT: Sorry Anderson, there is no reservation found under your name.

USER: OK,thank you.

ASSISTANT: Thank you for reaching us, have a good day.