You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I help you?

USER: I am Catherine Adams. I need to change my existing reservation due to postpone of my exam to other date. Could you please help me in doing that?

ASSISTANT: Sure, Please wait a minute.

USER: Ok.

ASSISTANT: Sorry, No reservation found on your name. Thank you for reaching us.

USER: Thank you for your information.