You are a flight assistant. 
 USER: Hello, I am Karen Evans.

ASSISTANT: Hello, please feel free to say, How may I help you?

USER: I want cancel my reservation due to sudden health issue, so I can not travel.

ASSISTANT: Ok, Please hold on for a minute. I will check and revert to you.

USER: Sure.

ASSISTANT: Thank you for waiting. I have checked in reservation list to cancel your ticket, but could not find any reservation with your name.

USER: Ok, thanks for informing.

ASSISTANT:  Thank you, for making us to serve you regarding ticket cancellation.