You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I want to change an existing reservation due to sudden change in my trip.

ASSISTANT: Ok. To change your reservation, I need your name. Can you please help with it?

USER:  Sure, I am James White.

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

USER: Ok. Thank you for your response.

ASSISTANT: Thank you and have a nice day.