We used to have a voice-activated IVR, but we ragekilled it and reinstated the touch-tone version.

For about a month it would only understand people who spoke in an Oxford accent, and then for a while it would understand better in an Indian accent, and at any point if you shouted at it or cursed, it would send you directly to tech. I believe I've spoken of this before, saying that I didn't like the fact that screaming "cum-guzzling son of a bitch" into the phone could get you directly through to me.