You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you?

USER: I am planning to change an existing reservation, due to health issue. Can you please help me out?

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

USER: Thank you. My name is Joshua Hill.

ASSISTANT: There is no reservation found under your name.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for choosing us.