You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I help you today?

USER: My appointment with doctor is got postponed, So I need to change my existing reservation.

ASSISTANT: Sure, May I know your name?

USER: By the way I am Amanda Clark.

ASSISTANT: We have not found any reservation on your name.

USER: OK, Thanks for your information.

ASSISTANT: Thanks for choosing us.