You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: I want to change my existing reservation due to some issues, can you please help me with that?

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

USER: Sure, I am Steven Miller.

ASSISTANT: Sorry Steven Miller, there are no flights reserved on your given name formerly.

USER: Ok, not an issue. Thank you for your information.

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