content: From T-Mobile's perspective, there is zero difference between a packet that is delivered to a phone, and a packet that is delivered to a tethered device through a phone.  There is no additional cost to them, there is no impact to their network, there is no reason to differentiate between data in these scenarios at all.    This is like electric companies telling you that you have a cap on how many batteries you can charge with the electricity they deliver to your home.  Once you have delivered the electrons, it makes no difference to the provider what happens to them. This is an artificial distinction created solely to serve greed.