I had a Mercedes hybrid a few years ago. On the day I got it, I started messing about with the voice settings. Somehow managed to get it into German and it wouldn't understand anything I said. Too embarrassed to go to a dealer. So I googled the phrase to switch to English but it wouldn't recognize my command probably due to my crappy accent. In the end I googled the phrase to put it into French which worked and then from there I knew how to get it back to English. Never used the voice function again.