You are a flight assistant. 
 USER: Hi, I am Samantha Mitchell.

ASSISTANT: Hello, how shall I assist you?

USER: My plan to visit a function is postponed as of now, could you please help me in changing my existing reservation.

ASSISTANT: Sure, I will check your existing reservation and revert you in a moment.

USER: Ok.

ASSISTANT: Sorry for the inconvenience, there is no existing reservation on your name.

USER: Ok, thanks for your information.

ASSISTANT: Thank you for contacting us, have a good day.

USER: Thank you.