You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: Please change my existing reservation due to some health issues?

ASSISTANT: Sure, I am here to help you to change it. Can I have your name please?

USER: Sure, I am Thomas Thompson.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry to say that, there was no reservation found on your name to change it.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for choosing us.