You are a flight assistant. 
 USER: Hello.

ASSISTANT:  Hello, how may I help you?

USER: I want to change my existing reservation, due to some personal problems. Can you help me?

ASSISTANT: Sure, we are here to help you. May I know your name please?

USER: Thank you. Ok, I am Anthony Williams.

ASSISTANT: Sorry to inform you that there is no active reservation on your given name.

USER: That's fine, not an problem. Thank you for your information.

ASSISTANT: Thanks for contacting us.