‘Free’ iPhone 7 offers from AT&T, Verizon, and others are basically two-year contracts

Every wireless carrier knows millions of people are trying to buy the iPhone 7 right now — and every one of them is using it as an opportunity to draw in customers. That’s why AT&T, Verizon, T-Mobile, and Sprint are all offering the extremely eye-catching opportunity to pick up an iPhone 7 for free. It sounds too good to be true. And, of course, it is. So here’s what the deal is when it comes to these free offers.

The first thing to know is that all of these free iPhone 7 offers require you to trade in a relatively new phone. In most cases that’s either an iPhone 6 or 6S, although Sprint, and in some cases AT&T, will also accept the Galaxy S7. Those phones will also have to be in good shape — so no broken screens. In most cases, you’ll also have to pay cash if you want an iPhone with more than 32GB of storage.

Trading in a phone is pretty par for the course here and hardly a secret. The big thing to know is that all of these deals essentially lock you into that carrier for two years. They’re basically a new spin on the old two-year contract, where you’d pay $200 for an iPhone so long as you agree not to leave the carrier. The difference this time around is that, instead of paying $200, you’re handing over a lightly used $650 phone.

(In theory, at least, your wireless plan is cheaper now than it was a few years ago, explaining the huge gap between those two payments; but you should check your bill to see if that’s actually the case.)

There are some big caveats that can turn a good deal into a very bad one

Once you agree to make the trade in, you’ll have to stick with that carrier for two years in order to actually get an iPhone 7 for free. If you cancel service, you’ll either have to give up the phone or pay off its full price, minus however much you’ve been credited on your monthly wireless bills. AT&T and Verizon only offer full payment, but T-Mobile and Sprint will also let you just hand the new phone back, too. It’s worth noting that in no case will you get your old phone back, so breaking the contract early on is a pretty bad idea.

Some other important caveats: some carriers take a few months to begin adding credits to your bill, which could keep you on the hook for longer. You’ll still have to pay taxes on the phone and likely some additional nonsense fees from the carrier ("activation fees" and whatnot) — so the phone isn’t going to be completely free.

So after all of that, are these actually good deals? They are this year, although with two big caveats. The first being, if you do cancel, this suddenly becomes a very bad deal — you lose your old phone and could be paying out close to full price for the new one. The second caveat being the flip side of that, you have to ready to stick with whichever carrier you choose for two years. That means being stuck with whatever plans and service they offer, good or bad.

Update September 9th, 1:10PM ET: AT&T updated its offer shortly after publication, opening it up to all customers; it was previously available only to DirecTV and U-Verse subscribers. Those subscribers now have a slightly different deal, which also lets them trade in the Galaxy S7 and allows the trade-in credit to be put toward other phones. The story has been updated to reflect this.