You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER:  I am Karen Smith want to change my reservation due to prepone of my meeting. Can you help me in changing?

ASSISTANT: Yes, I can help you. Give me a moment.

USER:  Ok.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: Thank you for your help.

ASSISTANT: Thank you for consulting us.