You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I want to change my existing reservation due to some health issues, can you help me with that?

ASSISTANT: Sure, we are happy to help you. Can you please let me know your good name?

USER: I am Joseph White.

ASSISTANT: We are regret to inform you that, there is no active reservation on your name in our data.

USER: No problem, thank you for the checking.

ASSISTANT: Thank you for availing us.