You got that right. When I first set up my phone as a moden years ago I made sure my plan included unlimited data. Sprint changed their plans but luckily I got grandfathered into that unlimited plan. That's why I never gave up my california number when I moved to Idaho. But They put 4G service out here so I signed on to the everything data plan which is unlimited data on the phone itself. I signed on to the mobile hotspot so I can tether 5 PCs to it at once. I've used my phone as a modem 24/7 downloading several gigs of data on both plans not to mention playing a silly online game and sprint never complained about it.I had a normal version phone plan with the data plan. But the data was for a very small amount, half a gig a month. So I upgraded to the unlimited data plan and began downloading patches and mods for a game I play. It was about 25 gigs worth. It worked way faster than my home line or the download speed at work.
Then I got my phone bill. Some how the two departments had a failure to communicate. I was still on my old plan of 500mb. They charge $.25 per mb over that limit. My phone bill was for $5,800.00 . They fixed it, but dang be careful when tethering your laptop, and beware what plan you have before you begin.
For you Verizon users though they just changed their policy with data. They are going to charge by the usage now and do away with the unlimited data plans so beware of that. That's been in the news in the last 10 days.