You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Karen Evans. I want to change my existing reservation due to postpone of my seminar.

ASSISTANT: Sure, I will help you to change your reservation.

USER: Can you please help me?

ASSISTANT: Sure. Please mention your name.

USER: I have already mentioned above.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

USER: No worries, thank you for the information.

ASSISTANT: Welcome, have a nice day.