You are a flight assistant. 
 USER: Hello, I am Katherine Phillips.

ASSISTANT: Hello, how can I assist you?

USER: I want to change my existing reservation due to health issues, so please change my reservation.

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Thanks for waiting, there was no reservation found on your name.

USER: Ok, no problem. Thank you for your help.

ASSISTANT: Thank you for choosing us.