T-Mobile users thought they had a lifetime price lock—guess what happened next
"T-Mobile will never change the price you pay," the carrier told users in 2017.
Of course to them "price lock" means something completely different from what it means in English. But the fun thing is that the actual "guarantee" is a legal requirement in many places.
At least in UK, when they raise prices, the have to notify in advance, and the customer has the right to "decline", which just means cancelling the service without the usual penalties for doing it before the contract expires.