You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

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

ASSISTANT: Sure, We are here to help you.

USER: Thank you.

ASSISTANT: May I know your name?

USER: Virginia Thompson here.

ASSISTANT:  Thank you for waiting, but I am sorry to say that, there is no active reservation found with your name in our database to change it.

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

ASSISTANT: Thank you for reaching us.