A voicemail only encourages them to call further. You could forward all calls (or simply forward on busy/reject) to a disconnected phone number. Alternatively,

A voicemail only encourages them to call further. You could forward all calls (or simply forward on busy/reject) to a disconnected phone number. Alternatively, some people say that if you put SIT tones ( https://en.wikipedia.org/wiki/Special_information_tone https://en.wikipedia.org/wiki/Special_information_tone ) on a voicemail greeting, that can help.