You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I am Joseph Davis. I am planning to change an existing reservation, due to health issue.

ASSISTANT: Sure, I am here to help you.

USER: Can you please change my reservation? Thank you.

ASSISTANT: Please be on hold.

USER: Sure.

ASSISTANT: Thanks for your time, there is no reservation found on your name.

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

ASSISTANT: Thank you for availing us.