IPhone 7 lock that prevents individuals from attempting to replace the home button on their own. Users are now required to go to an Apple Store to have repairs done, with "recalibration" of the button being necessary. This is a step further than Apple went with iPhone 5S, 6 and 6S, where only Touch ID functionality would get disabled but the "return-to-home" functionality still worked. Some iPhone 7 devices with the model numbers A1660, A1779 and A1780 suffer from a problem where they show a "No service" message even when cellular reception is available. Apple will repair those devices for free within
IPhone 3GS scheme from black on white to white on black, while Text Zoom allows users to zoom into a text on the screen. The iPhone 3GS retains the design of the 3G, with a glossy plastic back with tapered edges and metal buttons. The 3GS has reflective silver text on the reverse side which matches the silver Apple logo, replacing the 3G's grey text. Unlike its predecessor, the iPhone 3GS was available in white and black for 16 GB and 32 GB, although the 8 GB model was only available in black. Reviews of the iPhone 3GS have been generally mixed