You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you now?

USER: Can you please help me to change my reservation?

ASSISTANT: Sure, I am glad to help you with that.

USER: Thank you.

ASSISTANT: Can I know your name to check your previous reservation?

USER: Christopher Turner here.

ASSISTANT: Please wait a moment to check.

USER: Sure, take your time.

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

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for approaching us, have a great day.