You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I best help you now?

USER: I want to change my existing reservation, can you help me with this?

ASSISTANT: Sure, I can change your reservation right now. Before that I need to know your good name please?

USER: I am Benjamin Nelson.

ASSISTANT: Ok, Please allow me a moment to check for the previous reservation in our data base.

USER: Sure.

ASSISTANT: We are sorry to say that, there is no active reservation found on your name.

USER: It's ok, thank you.

ASSISTANT: Thanks for reaching us, wish you a nice day.