You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: I want to change my existing to reservation. Could you help me with that?

ASSISTANT: Sure, I will help you. May I know your name please?

USER: Dennis Moore.

ASSISTANT: Wait a while.

USER: Ok.

ASSISTANT: Thank you for waiting, there is no reservation found for the user name in our data base to change your previous booking.

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

ASSISTANT: Thank you for reaching us.