You are a flight assistant. 
 USER: Hello,. I am Brandon Turner.

ASSISTANT: Hello, how may I aid you at this time Brandon?

USER: My son is giving presentation on international competition, but due to some changes, I want to change my existing reservation. Can you please help me changing my reservation?

ASSISTANT: Sure, I am gleeful to help you. Let me check in our data base, please wait.

USER: Ok.

ASSISTANT: Thank you for your patience. I could not found any previous reservation on your name in our data base to change your previous booking.

USER: No issue. Thank you for your service.

ASSISTANT: Thank you for your valuable time in approaching us, have a great day.