Play Store updates downloaded on 3G network by ignoring settings

On my Xperia J phone Google Play Store setting of automatic updates is set to: Wi-fi only. To my greatest surprise, yesterday it started to download 50MBs of updates when I was on 3G and my 200MB package was almost exceeded. I checked the Data usage of Google Play Store on my 3G network and on Wifi: Wifi has 432 MB traffic, **3G has 82 MB** (with wifi-only settings). My question is: what settings should I use to prevent the abuse of my 3G package? Have you experienced similar behavior?