You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: Can you please change my existing details in my previous reservation?

ASSISTANT: Sure, I will help you.

USER: Thank you for opting my request.

ASSISTANT: Can you please provide your name to check your reservation?

USER: I have reserved my flight ticket in the name Brandon Roberts.

ASSISTANT: Please wait a moment to check. Sorry to inform you that, there is no reservation exists with your name in our records.

USER: Ok.

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

USER: Thank you.