You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: I want to change my reservation due to health problem, can you help me?

ASSISTANT: May I know your name please to proceed for ticket changing purpose?

USER: I am Daniel Roberts.

ASSISTANT: Let me check with that Daniel Roberts please give me a while.

USER: Sure.

ASSISTANT: Sorry to inform you that there is no reservation found in our database.

USER: No problem, thanks for checking.

ASSISTANT: Thank you.