You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you today?

USER: I am planning to change an existing reservation, due to heath issue. Can you please help me out?

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: Sure, my name is Barbara Jones.

ASSISTANT: Please be on hold.

USER: Sure.

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

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

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