• The new iPhone 7 will have a thinner iPhone 6-like design with redesigned antenna lines, new darker space black color option, dual camera, and redesigned force touch home button.

The new iPhone 7 will have a thinner iPhone 6-like design with redesigned antenna lines, new darker space black color option, dual camera, and redesigned force touch home button. (Photo : Facebook/Silk Innovation)

T-Mobile is also offering free iPhone 7 devices for those who want to preorder from the carrier provided they will trade-in their old iPhone 6 models for the newer smartphones from Apple.

There are already several carriers offering free iPhone 7s which does require a trade-in option from all of the iPhone 6 models available. The more expensive the model, the bigger the credit customers will receive that will show up on their monthly billing.

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Apple's iPhone 6 variants are not the only ones available for the trade-in option. T-Mobile customers can choose to trade their iPhone 5 models too for a $250 discount on the iPhone 7 and $370 for the iPhone 7 Plus, ZDNet has learned.

Users who currently have their iPhone 6 or iPhone 6 Plus phones would most likely benefit from just trading in their smartphones for a newer iPhone 7 instead of selling them to others. T-Mobile offers the iPhone 7 Plus for just $120 if a user manages to trade-in even just an iPhone 6.

Interested customers can also choose to preorder a larger iPhone 7 variant from T-Mobile but with an additional price. For instance, the iPhone 7 256GB model will need another $200 payment.

Customers need to know that the free iPhone 7 from T-Mobile or the other carriers are not exactly paid off in full once the iPhone 6 trade-in phone has been sent, The Verge reported. The credit will be rolled out every month and not in just one lump sum.

Another caveat is that customers will still need to pay off activation fees, taxes and whatnot that is included in the monthly billing. If the contract is locked for 24 months, customers will need to deal with such fees for two years which means the iPhone 7 is not exactly free as advertised in the preorder offers.

Interested parties can still apply for the iPhone 7 preorder offers from T-Mobile and the other carries. They just need to know all of the hidden fees besides the credit that will be given from trading in an iPhone 6, an iPhone 6 Plus or even an iPhone 5.