You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: Due to inconvenience of my work, I want to change my reservation. Can you please help me for that?

ASSISTANT: Sure, I am here to help you.

USER: Thanks.

ASSISTANT: May I know on whose name the ticket has been reserved formerly?

USER: My name is Gary Hill.

ASSISTANT: Sorry Gary Hill, there are no flights reserved on your given name formerly.

USER: Anyway, thanks for the information.

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