I'm on unlimited data here for a new note 4 that I had upgraded to, and have used 864MB of data. My speed tests run literally less than .5mb/s for both upload and download. This ocurrs no matter where I am, and I had never had this issue in the past. It only ocurred when I recently upgraded from my note 2 to my note 4, in which the sales rep tried to get me to "save money" by getting off unlimited data.
So yes, I would say that they do throttle you once someone actually does take a look at how much data you use and if you are on unlimited data. Power cycling, resetting my settings, nothing solves the below .5mb/s up and down rates, more so reinforced by the fact that hopping on my wifi shoots the speeds up to 25+ for up, 4+ for down.