You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Catherine Allen. I need to change my recent reservation due to postpone of my exams. Could you please help me in doing that?

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your given name.

USER: No problem, thank you for your information.

ASSISTANT: Thank you for choosing us.