You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: I am Deborah Lewis. I want to change my existing reservation. Could you help me?

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

USER: Thank you.

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

USER: That's ok, no problem. Thank you.

ASSISTANT: You are welcome.