You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Katherine Mitchell.

ASSISTANT: How can I assist you today?

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

ASSISTANT: Sure, will you please give me a moment?

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation found under your name.

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

ASSISTANT: Welcome, have a great day.