You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

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

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

USER: Sure, I am Gary Hall.

ASSISTANT: Gary Hall, we haven't  found any reservation under your name in our database.

USER: Ok, not an issue. Thank you for choosing us.

ASSISTANT: Thank you for choosing us.