You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Mary White.

ASSISTANT: How can I help you?

USER: I am planning to change an existing reservation, due to some exams. Can you help me out?

ASSISTANT: Your flight ticket is not reserved before.

USER: Thant's fine.

ASSISTANT: Thank you for contacting us.

USER: Thank you for your time.