You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: Myself Timothy Lopez. I want to change my existing reservation, can you help me in that?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

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

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

ASSISTANT: You are welcome.