You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you today?

USER: I am Kenneth Williams. I would like to change my existing reservation. Could you help me out?

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

USER: Glad to hear that.

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

USER: Ok, no problem. Thank you for the information.

ASSISTANT: You are welcome always.