You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you for today?

USER: Can you help me to change my existing reservation?

ASSISTANT: Sure, may I know your name to check the details of your reservation?

USER: Yes, my name is Andrew Collins.

ASSISTANT: OK Andrew, please wait for a moment.

USER: OK.

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

USER: OK, thank you.

ASSISTANT: Thank you for approaching us.