You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I'm Alexander Brown here, I want to change my existing reservation. Can you please help me?

ASSISTANT: Alexander Brown, I am here to help you. Please wait a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found with your name.

USER: Ok, that's fine. Thank you for your kind information.

ASSISTANT: Thank you and have a great day.