You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: I need to change my existing reservation due to my conference has been postponed. Can you please assist me to change it?

ASSISTANT: Sure, I am here to help you. May I know on whose name the ticket has been booked formerly?

USER: Thank you, Please check my reservation on the name of Pamela Hall.

ASSISTANT: Sorry Pamela Hall, there are no flights reserved on your given name formerly.

USER: That's Ok, thanks for your assistance.

ASSISTANT: Welcome, thank you for choosing us. Have a great day.