You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Christine Clark.

ASSISTANT: Christine Clark, how may I assist you today?

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

ASSISTANT: Sure, I will help you. Please allow me a minute.

USER: Thank you.

ASSISTANT: Christine Clark, I am really sorry to inform you that there is no active booking on your name.

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

ASSISTANT: Thank you for reaching us. Have a great day.

USER: Welcome.