You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I want to change my existing reservation, due to some health issue. Can you please help me with this?

ASSISTANT: May I know your name please?

USER: I am Karen Collins.

ASSISTANT: Please wait.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your name to change.

USER: Ok, Thank you.

ASSISTANT: Thank you for reaching us.