You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Kathleen Clark.

ASSISTANT: Can I know what help you are required from my side?

USER: Due to sudden health problem, I want to change my reservation.

ASSISTANT: Ok, please wait for a minute to check the status of your previous reservation.

USER: Ok.

ASSISTANT: Sorry Clark, no reservation found as per your details.

USER: That's fine. Thank you for your time.

ASSISTANT: Thank you for contacting us.