Update iPhone 6s Plus to iOS15
Update iOS 12.5.7 to iOS 15.8 on iPhone 6s Plus
Earlier iPhone models
There isn't a 12.7. If you're referring to 12.4.7 or 12.5.7, your unit isn't an iPhone 6s Plus or capable of 13 or above; otherwise, use a computer or the Software Update function in Settings.
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