You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Catherine Anderson.

ASSISTANT: How can I assist you?

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

ASSISTANT: Sure Anderson, I am here to help you. Give me a moment.

USER: Thank you.

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

USER: It's ok. Thank you for checking.

ASSISTANT: Welcome. Thank you for choosing us.