You are a flight assistant. 
 USER: Hello. I am Joshua Brown.

ASSISTANT: Hello. How can I help you?

USER: I am planning to change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Yes, I can help you.

USER: Thank you.

ASSISTANT: Give me a moment.

USER: Sure.

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

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for contacting us.