You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

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

ASSISTANT: Sure, please wait a moment I will check your reservation details and proceed further.

USER: Sure, I will wait.

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

USER: That's fine.

ASSISTANT: Thank you for reaching us, have a nice day.

USER: Thank you for your service.