The point of the bandwidth restriction is to limit the amount of data you are able to use.
So a bandwidth limit is a limit on data volume by restricting speed.
A 4G unlimited data plan means unlimited amount of data at average 4G speeds.
So, when you signed up for "Unlimited Data", it was back in 2007 if you were with AT&T. They canceled within months of offering it. As a courtesy, (NOT by contract), they let you stay with unlimited. So now for very smart reasons that most of the rest of us appreciate, they would prefer you get a real plan. Because you won't, they limit you to that 2007 data speed. Your throttled speed is probably way faster than what you would have gotten on the first iPhone. EXTREMELY reasonable.
The rest of us who have real plans are very happy that these carriers are throttling. It prevent network slowdowns. Why should someone who bought a plan 6 or 7 years ago get special treatment?
Keep complaining and they will just give you a new plan or watch you walk. And the only place to go is to another carrier who will not give you unlimited. (or if they do, it will be throttled by default because they suck).
And for the record, this statement "A 4G unlimited data plan means unlimited amount of data at average 4G speeds" is what you WANT unlimited data plan to mean. It is not what it means in your contract.
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I can guarantee by throttling the one unlimited user on that so called congested tower, who just happens to hit the magical 5GB number, will not suddenly speed up the service for all the rest. We all know that is BS. Simple as that. Because at any one time on a congested tower, you probably will not have more than one user with unlimited who hit the 5GB limit. Most of the time, you probably have none, and the congested tower is not the result of unlimited data users. It's a scam by Verizon, and I'm glad the FCC sees through that.
#1 You can't guarantee anything. You get discredited when you start your argument that way.
#2 They are throttling WAY WAY WAY more than one user (you).
#3 Its not all about you. The network is for all users.
#4 You are NOT buying UNLIMITED BANDWIDTH and the contract for both AT&T gives them the right to throttle you. READ IT
#5 If the government sticks their hand in it, unlimited plans will be gone immediately. They will not just decide to give you unlimited data and unlimited bandwidth. They will cancel your plan and make you pick one like you should have a few years ago.