You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I support you today?

USER: I am Joshua Lopez. Due to postpone of my exams, I would like to change my existing reservation.Could you please aid me in changing?

ASSISTANT: Sure, we are happy to help you. Please hold for a while.

USER: Sure.

ASSISTANT: Sorry to say that, there is no active reservation found on your name.

USER: Ok, no problem.

ASSISTANT: Thank you for opting us.

USER: Thank you.