You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you?

USER: I am Rachel White.

ASSISTANT: Hope you are doing well Rachel White.

USER: Actually, I want to change an existing reservation, because of health  issue. Can you help me out?

ASSISTANT: Sure, I am here to help you. Sorry, there is no previous reservation found on your details.

USER: Thank you for your help.

ASSISTANT: You are welcome.