You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Due to sudden change in my exam dates I need to change my existing reservation.

ASSISTANT: Sure, I am glad to help you with that.

USER: Thank you.

ASSISTANT: May I know your name for the further process?

USER: I am Donna Hall.

ASSISTANT: Sorry to tell you, there is no previous reservation found under your name.

USER: No problem. Thank you for the information.

ASSISTANT: Donna Hall, thank you for choosing our agency. Have a great day.