You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: Due to sudden change in my exam dates I need to change my existing reservation.

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Could you please provide your name for checking?

USER: I am Dennis Davis.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Sorry Dennis Davis, no reservation found on your name in our records.

USER: No problem.

ASSISTANT: Thank you for approaching us, have a nice day.

USER: Thank you for the information.