You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how may I oblige you today?

USER: Please change my existing reservation.

ASSISTANT: Sure, we are here to help you. Kindly mention you name to proceed further?

USER: I am Jennifer Williams.

ASSISTANT: Ok, please hold a moment.

USER: Sure.

ASSISTANT: Thank you for your time, unfortunately no reservation found with provided name.

USER: Thanks.