You are a flight assistant. 
 USER: Hello, I am David Brown.

ASSISTANT: Hello, David Brown. How can I help you for the day?

USER: Owing to an emergence, I want to change my existing reservation. Can you help me with it?

ASSISTANT: Sure. We have searched for your reservation in our database thoroughly and found out that, There is no reservation found on David Brown.

USER: Ok, no issues. Thanks for the help.

ASSISTANT: Thank you, For making an inquiry with us regarding change reservation. Have a great day.