James Martin/CNET

With the new iPhones set to go on preorder Friday, the usual "buy one, get one" deals are starting to pop up from carriers and retailers. These deals are nothing new, offering hefty discounts if you're willing to switch providers or add a new line to your wireless account. While this is good for people thinking of switching, it never helps those who have the lines they need and are just looking to upgrade their phone.

As it has in recent years, T-Mobile is doing something different, offering potential savings of 50% or more to current customers who trade in their iPhone and get a new one from the carrier on its 24-month installment plan.

T-Mobile says you can trade in an iPhone 7 and get half off the $699 iPhone 11. Trade in an iPhone XS Max and get half off the $1,099 iPhone 11 Pro Max.

DUE FOR AN UPGRADE??? 🤔🤔



YOU KNOW WHERE TO GO!!! @TMOBILE!!



TRADE IN YOUR OLD #IPHONE AND GET UP TO 50% OFF THE NEW IPHONES ❗️❗️



THIS DEAL IS SO GOOD I CAN’T STOP TWEETING IN ALL CAPS!!! pic.twitter.com/RaPBSS9fza — John Legere (@JohnLegere) September 12, 2019

The iPhone 7 deal is actually better than Apple's own iPhone trade-in offers, which only knocks off $150 when trading in that device for an iPhone 11. Trading in an iPhone XS Max for an iPhone 11 Pro Max seems to be better at Apple, which will knock $600 off the price of an iPhone 11 Pro Max to take the $1,099 phone down to $499.

Here's the full pricing break down from T-Mobile: Save $550 when you trade in an iPhone XS Max 64GB or 256GB; save $500 when you trade in an iPhone XS 64GB or 256GB; and save $350 when you trade in an iPhone XR 64GB or 128GB, X 64GB, 8, 8 Plus, 7 or 7 Plus.

The offer will apply to those looking to buy an iPhone 11, 11 Pro, 11 Pro Max, XR, XS or XS Max. As with other deals, taxes and fees are due at the time of purchase and you must trade in your older iPhone in good condition within 30 days of your new phone's shipment if you order online (you can also trade in immediately if you buy in-store).

T-Mobile says that there is no requirement to be on its newer Magenta plans to get the deal.

Now playing: Watch this: iPhone 11 Pro vs. iPhone XS: Flagship phones compared

Canceling service before you fully pay off the phone will put you on the hook for the outstanding balance, though T-Mobile says those who want to cancel should "contact us before canceling to instead make discounted monthly balance payments."

As with last year's iPhones, the new iPhone 11 models support T-Mobile's latest 600MHz (band 71) spectrum that works significantly better indoors. The company says this new spectrum reaches twice as far as its prior network and "penetrates walls for 4x better coverage in-buildings."

Even after years of growth and improvements, T-Mobile is still trying to shake off a reputation for being a lower class network compared to Verizon and AT&T and it's hoping that getting more people onto this improved network could go a long way in continuing to change that narrative.

This improved lower spectrum is also behind T-Mobile's latest "Test Drive" offer that gives people interested in trying out the carrier's network a free hotspot and 30GB of data to use in 30 days.

Originally published Sept. 12, 6:20 a.m. PT.

Update, 12:29 p.m.: Adds details on plans.