You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: I want to change my existing reservation, as my health is not good to travel. Can you please help me with this?

ASSISTANT: Yes, I can help you. Give me a moment. Can I know your name for checking your previous reservation?

USER: I am Gregory Robinson here.

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

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your assistance.