Re: Unlimited doesn't mean unlimited then...
Although I largely don't agree with the nonchalant way carriers throw around the word "unlimited" nowadays, T-Mobile clearly defines it.
If you look at their FAQ:
Doesn’t Unlimited mean Unlimited? How can T-Mobile advertise Unlimited 4G LTE when T-Mobile doesn't offer it on all T-Mobile devices?
Yes, at T-Mobile, unlimited mean unlimited. Every T-Mobile Simple Choice™ Plan includes Smartphone Mobile HotSpot at no extra charge, and when customers reach their paid high-speed data allotment, speeds are reduced so they never worry about overages. Our standard Unlimited 4G LTE smartphone plan includes unlimited high-speed data on your smartphone and also comes with 7 GB high-speed Smartphone Mobile HotSpot data, followed by unlimited reduced-speed Smartphone Mobile HotSpot data.
Regular, non-tethered 4G LTE is unlimited. The ability to use your phone as a hotspot is an add-on they give you for free. They're also talking about people who are deliberately circumventing the check put in place to avoid people abusing the free tethering.
For comparison, I am on a grandfathered AT&T unlimited data plan, but I don't have any (legal) tethering allotment, because that's a paid add-on.