Hey, feature idea - riffing off the now overdue but unlikely to happen call flag for non-human callers, how about a voice-recognised audio-captcha before you're put through during open hours?
This is also why your average big-company automated attendant is so bad at interpreting what you want outside of the 5 common things people want to talk about (most of which I can do online, so it's never what I'm there for) and again sadly only if you're in the more common US American English accent pool. Southern accents tend to get squelched pretty bad and that's just the beginning of accents common in the US.
One could conceivably target an individuals desired accent recognition so you could let the user say "Most of my callers speak in an X accent" and then get a little more accurate for that pool of callers, but this also means installing disparate systems for recognition, each of which are quite expensive computationally.
This is a deeply interesting problem space, though, and if you're interested there's quite a bit of discussion over it in the sphinx project and several research communities.