You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I am Richard Nelson. I need to change my existing reservation, Can you please help me that?

ASSISTANT: Sure, we are to help you. Please wait a moment.

USER: Sure.

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

USER: Ok, no probloem. Thanks for your information.

ASSISTANT: Thank you for choosing us.