You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: I just want to change my existing reservation, because of postpone of my examination at Boston.

ASSISTANT: Ok, may I know your name?

USER: Myself Alexander Wright here.

ASSISTANT: Ok Wright, wait a moment.

USER: Sure.

ASSISTANT: Wright, unfortunately there is no reservation found under name.

USER: That's fine. Thank you for your information.

ASSISTANT: Welcome. Thank you for choosing us.