You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Sure, I can help you in this problem.

USER: Thank you.

ASSISTANT: Please may I know on whose name the flight ticket was booked?

USER: Samantha Brown here.

ASSISTANT: You have to wait for a moment as I have to search for your flight reservation.

USER: Ok.

ASSISTANT: Thanks for waiting. Sorry to say that I could not find your flight ticket reservation to change it.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you.