Right - BYOD (I called it "paying for your device in full" since you could have gotten the device from the carrier).

I'm sure you know better than I would, but most people who are holding on to the unlimited data plan don't actually use more data than the standard plans allow these days. Plus, last I looked into it, the unlimited data grandfathered plans didn't allow tethering, which, for many of us, is an essential feature these days.