You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Catherine Collins. I am planning to change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Sure Collins, please wait a moment.

USER: Sure.

ASSISTANT: Sorry to say that, there is no reservation found on your name.

USER: That's fine.

ASSISTANT: Thank you for approaching us.

USER: Thank you for your help.