I currently have an HTC One, and I've used the Mobile Hotspot feature on it a couple of times. I have the $70 unlimited plan, and I know they include 500 MB of data for hotspot usage, and you can track this with the My T-Mobile app, or at my.t-mobile.com. The interesting thing is, when I check this usage, I still show it as 0.00/500.00 MB of hotspot data used. I've connected both my iPod Touches to this thing, and a Macbook Pro, did a little bit of surfing and app updating, checked again and it's still 0. It doesn't seem to matter whether I'm LTE or HSPA+, and whether I do Mobile Hotspot or Bluetooth sharing. Here is a picture of my usage; has anyone else noticed this, too?