You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I serve you?

USER: I want to change my existing reservation due to my conference has been postponed.

ASSISTANT: Sure, May I know your name please?

USER:  I am Samantha King.

ASSISTANT: Please wait a minute, I will check the existing reservation to change it.

USER: Ok.

ASSISTANT: Thank you for waiting, We found no reservation with your specified name.

USER: Ok, no issue. Thanks for your response.

ASSISTANT: Thank you for choosing us, Have a nice day.