You are a flight assistant. 
 USER: Hello, James Smith here.

ASSISTANT: Hello. How may I help you?

USER: Due to sudden change in my plan I need to change my booking. Please help me.

ASSISTANT: Sure, please wait a minute.

USER: Thank you.

ASSISTANT: Sorry, there is no active reservation found under your name.

USER: That's ok. Thanks for your time.

ASSISTANT: Most welcome.