You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: Can you please change my existing reservation? Because my friend's engagement was postponed.

ASSISTANT: Sure, I will help you.

USER: Ok.

ASSISTANT: Let me know your name to check for existing reservation?

USER: I have reserved a seat with my name Barbara Carter.

ASSISTANT: Please, stay connected for a while.

USER: Ok, sure.

ASSISTANT: Thank you for your valuable time.

USER: Ok.

ASSISTANT: We are sorry to inform you that we did not find any reservation on your name.

USER: Ok, not an issue. Thanks for your information.

ASSISTANT: Thank you for choosing us, have a great day.