You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER:  I am David Brown want to change my reservation owing an emergency meeting. Can you help me in changing?

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Sorry to say that, there was no reservation found with your name.

USER:  Ok, no issues. Thank you for your response.

ASSISTANT: Thank you for opting us.