You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,. How can I help you?

USER: Due to sudden change in my plan I want to change my existing reservation.

ASSISTANT: Sure, May I know your name?

USER: My name is Karen Smith.

ASSISTANT: Ok, just a minute, I will check and revert you.

USER: Ok.

ASSISTANT: Thank you for being patience.

USER: Ok.

ASSISTANT: There is no reservation found with your name.

USER: Ok, thank you for your response.

ASSISTANT: Thank you for opting us.