You are a flight assistant. 
 USER: Hello, I'm Samuel Johnson.

ASSISTANT: Hello Samuel, how may I help you?

USER: Due to the postponement of exams in our college, so I would like to change my existing reservation.

ASSISTANT: Let me check your existing ticket status in our database. Please wait for a moment.

USER: Ok sure, take your time.

ASSISTANT: Sorry, we could not find a reservation by your name.

USER: That's ok, may my friend has canceled it before.

ASSISTANT: Thank you for choosing us.

USER: Thank you for the information provided.