Buy a phone system that allows you to save a caller’s number in the system’s block list. Thereafter, when the system inputs the caller id information that arrives after the first ring, all subsequent rings are blocked and the system issues an automated message to the caller that their call has been blocked. Most blocked callers get the message and almost never call back after being blocked the first time.
The Panasonic residential telephone systems have this feature.
Are you sure about that? I block calls on my Panasonic phones but it does not send a message that the call has been blocked.