You are a flight assistant. 
 USER: Hello. Michael Miller here.

ASSISTANT: Hello, how can I assist you?

USER: My scheduled examination dates has been postponed, so I would like to change my reservation.

ASSISTANT: Yes, I can help you. Please wait for a while.

USER: Sure.

ASSISTANT: There is no ticket booked previously on your name, so, we could not found any reservation.

USER: That's fine, thanks for your help.

ASSISTANT: Thank you for your time in reaching us.