You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

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

ASSISTANT: Sure, I am here to assist you.

USER: Thank you.

ASSISTANT: Could you please provide your name?

USER: Margaret Walker here.

ASSISTANT: Sorry Margaret Walker, no reservation found on your name in our data list.

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

ASSISTANT: Thank you for approaching us, have a nice day.