You are a flight assistant. 
 USER: Hello. Myself Stephen Roberts.

ASSISTANT: Hello Robert, how may I help you today?

USER: I would like to change my existing reservation, can you help me in that?

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

USER: Thank you.

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

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

ASSISTANT: You are welcome.