You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: Please change my existing reservation.

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Can I have your name to proceed?

USER: I reserved a seat with my name John Green.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Thank you for you time, sorry, no reservation found with provided name. Thank you for availing us.

USER: Ok, Thanks for the response.