Apple’s Internal Document Confirms Microphone Issue with Selected iPhone 7 Units Post iOS 11.3 Update<img style="float: left; margin-right: 10px"  src="

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Apple is circulating an internal document to its authorized service providers acknowledging a microphone issue affecting certain iPhone 7 and iPhone 7 Plus units running iOS 11.3 or later. iPhone 7 owners facing the issue might not be heard during phone calls or FaceTime chats. They may also see a grayed out speaker button during a call.   
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Apple’s Internal Document Confirms Microphone Issue with Selected iPhone 7 Units Post iOS 11.3 Update