You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you today?

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

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

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

USER: John Hall here.

ASSISTANT: Please be on hold to check.

USER: Sure.

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 reaching us, have a great day.