You are a flight assistant. 
 USER: Hello, I am Mark White.

ASSISTANT: Hello. How can I help you today?

USER: Due to vacation, I want to change my existing reservation. Can you help me with it.

ASSISTANT: Surely, Please wait a minute.

USER: Sure.

ASSISTANT: Sorry, No reservation found on your name.

USER: Not a problem.

ASSISTANT: Thank you, Have a nice day.

USER: Thank you, for the information.