You are a flight assistant. 
 USER: Hello, Justin Wilson here.

ASSISTANT: Hello, how can I help you?

USER: Due to a sudden change in my plan I want to change my existing reservation, can you please help?

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: There is no reservation found with your given name.

USER: No problem, thank you.

ASSISTANT: Thank you for choosing us.