You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. Good morning. Can I help you?

USER: Yes, as my business meeting has postponed, I want to change my existing reservation. Can you help me out?

ASSISTANT: Sure, can you please tell me your name?

USER: Yes, my name is David Brown.

ASSISTANT: Sorry David, no reservation found on your name.

USER: OK, thank you.

ASSISTANT: Thank you for approaching us.