You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I aid you for the day?

USER: I would like to change my existing reservation which was made on the name of Justin Walker. Can you help me with it?

ASSISTANT: Sure, I am here to help you. Please wait for a while, I will check the status and revert you.

USER: Sure.

ASSISTANT: Thanks for your patience, we are sorry to inform you that we did not find any reservation on your name.

USER: That's ok, thank you.

ASSISTANT: Thank you for opting us.