Oh, so they are really like the old AOL. Back in the 1990s, they would give you 1050 free hours... during the first month of service. Only problem, 1050 hours is more than the actual number of hours in a month. So TMobile is really saying come here for the unlimited data, which they really push, but in the smaller print, only 7GB of that can be used for tethering. When they very well know most people who see that unlimited want it for tethering as a big selling point.
It's all data. Just stop playing games.