You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you?

USER: I am Barbara Clark. I change my existing reservation. Could you please help?

ASSISTANT: Sure, please hold on for moment.

USER: Sure, please take your time.

ASSISTANT: I am sorry, there are no reservations found.

USER: Ok, no problem. Thank you for the information.

ASSISTANT: Thank you, have a good day.