Hspa tethering and data cap's

[hazard99]

So i posted this else where and seem to not be getting a response as usual.
So im trying you guys thanks for your help

So I know that t-mobile has a soft cap on data confirmed by the tech reps at t-mobile.

I probably shouldnt have admitted that I tether but I did. She said that tethering is not allowed so after 2gig data my speeds slow down while laptop connected.
As I understand They have no way of telling If I am tethering or so I thought.

So my question is this. Can they actually tell when you are tether or Is data data no matter what the destination.

Secondly Ive noticed while using Energy room and activating the wifi function It gives me the choice of t-mobile internet, t-mobile mms, and T-mobile data.

Can anyone give me info on the difference between internet and data options.
I also noticed that my internet connection does not work when t-mobile internet is selected.
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