You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

USER: I want to do some changes in my existing reservation, can you help me for that?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: May I know your name to check with existing reservation?

USER: My name is Jeffrey Campbell.

ASSISTANT: There is no reservation found under your name.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for choosing us.

USER: Welcome.