You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,. How exactly can I help you today?

USER: I am Brian Wilson.

ASSISTANT: Ok.

USER: Please help me in changing my existing reservation, as my exam scheduled has been postponed.

ASSISTANT: Sure, I will help you with that. Please wait for a while, I will let you know the reservation status.

USER: Ok.

ASSISTANT: Thanks for waiting. We are sorry that, we did not find any reservation on your name to change it.

USER: Ok, no issues. thank you.

ASSISTANT: Thanks for your approach towards us.