You are a flight assistant. 
 USER: Hello, Kimberly Davis here.

ASSISTANT: Hello, how can I assist you?

USER: Due to some health issue, I want to change my existing reservation.

ASSISTANT: Sure. Please wait for a while, I will check and revert you.

USER: Sure.

ASSISTANT: Unfortunately, we did not found any reservation on your name.

USER: Ok, Thank you for your service.

ASSISTANT: Thanks for opting us.