You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: I want to change my existing reservation, Can you please help me in that?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

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

USER: My name is Mary Scott.

ASSISTANT: Sorry Mary Scott, there are no flights reserved on your given name formerly.

USER: Ok, that's not a problem. Thanks for your information.

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