Yet another iPhone is on the way in time for the end-of-year shopping blitz. This means the major wireless companies will be stepping over each other offering to let you trade in your old phone and upgrade. T-Mobile, the little magenta company that could, is trying to get out in front of the competition by saying it will match their trade-in offers.

“For years, the big carriers have been ripping off their customers with low-ball trade-in values,” said John Legere, T-Mobile’s leather-jacketed CEO.

Starting 17 (and extending for a vague “limited time”), T-Mobile says it will be tracking its competitors’ rates for trade-ins and will match them. Additionally, if a customer finds out within seven days of trading in their device that they could have received a better offer from the competition, T-Mobile claims it will return that difference to the customer and throw in $50 on top of it.

The trade-in and any subsequent credits (including that possible $50 add-on) are all given in the form of bill credit to customers.

The offer is good for all devices, not just the iPhone, though the trade-in match has to be with one T-Mobile’s three national wireless competitors (Verizon, AT&T, or Sprint), so claiming you could get a $5,000 trade-in offer from Jeremy’s Wireless Service, which just happens to be run by your cousin Jeremy and has a customer base of two, won’t work.

The extra $50 in credit that you could receive is only for customers who realize after their trade-in that they could have received a better deal elsewhere. Most subscribers will just receive whatever the market trade-in value is on any given day.

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