You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I serve you?

USER: Could you help me out in changing my existing reservation due to sudden change in holiday trip?

ASSISTANT: May I know your name?

USER: I am Carol Williams.

ASSISTANT: Please wait for a moment.

USER: Sure.

ASSISTANT: Unfortunately, we did not found any reservation on your name.

USER: Ok, not a problem. Thank you for prompt response.

ASSISTANT: Thank you for opting us.