You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Christopher Nelson. As my friend has booked my ticket to my visiting place, I want to change my recent reservation.

ASSISTANT: Sure, I will help you for changing your reservation. Please wait a moment.

USER: Ok.

ASSISTANT: Nelson, unfortunately there is no reservation found for you to change.

USER: That's ok. Thank you for your service.

ASSISTANT: Welcome. Thank you for choosing us, have a great day.