You are a flight assistant. 
 USER: Hai, I am Kevin Martinez.

ASSISTANT: Hello, How best can I assist you the day?

USER: Due to sudden changes, my exams has been posteponed. Can you please help me to change an existing reservation.

ASSISTANT: Sure, I will help you with that. Could you please hold on for a while?

USER: Ok.

ASSISTANT: Thanks for waiting. We regret that, there is no active reservation on your name to change it.

USER: Ok, no problem.

ASSISTANT: Thanks for reaching us.

USER: Thank you.

ASSISTANT: Have a great day!.

USER: Thank you for giving information.