You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

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

ASSISTANT: Sure, I am here to help you out. May I know your name please?

USER: Brian Phillips.

ASSISTANT: Brian Phillips, we haven't found any reservation under your name in our database.

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

ASSISTANT: Thank you for choosing us.