The fires that spread over the internet over the past week about the forced plan changes has now led to CEO Mike Sievert issuing an email to employees.
Say you've signed a 1-year contract with a provider and 6 months in they say they're migrating plans and raising the price. Would that go into effect immediately or at the end of your contract?
If immediately, would that allow you to legally end the contract without paying fees to do so?
This is part of the reason they did that long game of, "Look, no more phones tied to contracts! No contracts!" They say in the terms of service that you can't sue, you have to go to mediation.
So, since the phones are on monthly installment loans that aren't attached to the service plan, and the company says any beef you have has to go through mediation, basically means they can change whatever they want whenever they want on the plans. If you don't like it, you're free to leave your plan! Your plan payments would cut off at time of exit, you and the carrier part ways.
However, since the terms of the phone loan indicate that termination of your plan means the entirety of the phone loan is immediately due, you still have to pay off the phone, as it is no longer considered to be part of the phone plan.
T-Mobile looked like they were above-board the last 3 years because the government required that they don't manipulate plans for at least 3 years after the merger. The three years is up, and they're now playing various games to see how they can change plans in ways that are legal.