You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I aid you today?

USER: Nancy Walker here. I want to change my existing reservation due to postpone of my exams. Can you help me in that?

ASSISTANT: Sure, we can help with that.

USER: Thank you.

ASSISTANT: Please wait for a moment.

USER: Ok.

ASSISTANT: Thank you for waiting, there is no active reservation found with the given name.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for opting us.