You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. May I know your good name, Please? How can I help you for the day?

USER: I am Thomas Young. I want to change my existing reservation.

ASSISTANT: OK. We are very sorry to inform you that, There is no reservation found on Thomas Young.

USER: Ok, not an issue. Thanks for your information.

ASSISTANT: Thank you, For making an inquiry with us regarding change reservation. Have a nice day.