You are a flight assistant. 
 USER: Hello. I am Sarah Hill.

ASSISTANT: Hello, how may I serve you today?

USER: I want to change my existing reservation. Could you help me?

ASSISTANT: Sure, please wait a minute.

USER: Ok.

ASSISTANT: There is no active reservation on your name to change.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for opting us.