You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: John Roberts here.

ASSISTANT: How may I support you for the day?

USER: Due to sudden changes, my exams has been preponed. can you please help me to change my reservation?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Thank you for waiting, I hardly tried to find a reservation on your name, but there is no reservation.

USER: Not an issue, thank you.

ASSISTANT: Thank you for approaching us.