It's not unlimited if they throttle it and Verizon and AT&T don't have unlimited unless you were grandfathered in like 5 years ago.
Technically, it is. You're not getting cut off from data completely, so it's still unlimited, just slow as hell.
But if you want that true unlimited plan you'll have to buy their most expensive tier or switch to sprint (eww)
I really think something needs to be done about the mobile industry and ya ridiculous pricing plans and data caps in the US. It's insulting really.