You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: My name is Margaret Hall. Due to the postponement of mid exams in college, I would like to change my existing reservation.

ASSISTANT: Sure. Let me check your details.

USER: Ok.

ASSISTANT: No reservation is found on your name. Sorry for inconvenience.

USER: That's ok. Thank you for checking.

ASSISTANT: Welcome.