You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Anthony Collins.

ASSISTANT: How can I assist you?

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

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT: Sorry, no reservation found on your name to change.

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

ASSISTANT: Thank you for reaching us..