You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: Due to sudden change in my trip I need to change my existing reservation. Can you help me changing my existing reservation?

ASSISTANT: Sure, I am here to help you with this.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: I am Patricia Martinez.

ASSISTANT: Sorry Martinez, there is no reservation found as per your name to change it.

USER: No problem. Thank you for the information.

ASSISTANT: You are welcome always.