You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I am Stephen Parker. I want to change my existing reservation. Could you help me with that?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to say that, there was no reservation found with your name.

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

ASSISTANT: Thank you for opting us.