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.
@arstechnica We joined early last year and our price went up a couple times. They were good under John Legere. I don’t even know who’s driving the bus now.