You are a flight assistant. 
 USER: Hello, Paul Brown here.

ASSISTANT: Hello Brown. How may I assist you today?

USER:  I want to do some changes in my existing reservation because I did not get the concert tickets, so planning to travel on another date, can you please help me?

ASSISTANT: Sure. In my database I did not found any reservation with your name.

USER: Ok, no issues.

ASSISTANT: Thank you for contacting us.

USER: Thank you for giving information.