Beware these gotchas in T-Mobile's 'free' iPhone 7 offer

Want a free or heavily discounted Apple iPhone 7? If so, T-Mobile has an offer for you. But as always, you need to read the fine print, because it has a few gotchas.As part of T-Mobile's Black Friday offer, you can trade in a qualifying used smartphone and get a 32GB iPhone 7 for free, or get the larger iPhone 7 Plus for $100. Those devices normally cost $649.99 and $769.99 respectively. (Similar deals are available for Samsung and LG phones, as well.)To read this article in full or to leave a c