You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I serve you?

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

ASSISTANT: Sure, I am here to help you. May I know your good name?

USER: Thank you. I am Christopher Turner.

ASSISTANT: Sorry, we did not find any active reservation on your name in our records.

USER: Ok, not an problem. Thank you for your help.

ASSISTANT: Thank you for contacting us.