Apple would have instructed its employees in service stores to repair iPhones if customers come forward with reports of microphone problems after installing iOS 11.3. For the time being there seems to be no software-based solution.
The first thing Apple employees should try when a customer comes to report problems is disconnecting any bluetooth devices. If that does not work, the diagnostic software must be started up. According to the internal document, the iPhones with problems give the message “device could not detect dock” or “accessory not supported”. If these error messages are displayed, the iPhone needs to be repaired.
How this is being repaired is not clear, but it does not seem to be a software update. Therefore, it is not yet known whether Apple with a new version of iOS the problems with the microphone dissolves. The cause of the bug is also still unknown.
It does not appear that the microphone problems occur with every user of an iPhone 7 or iPhone 7 Plus. According to MacRumors, users have been reported in several places, including Apple’s forums. But the problems in iOS 11.3 seem to affect only some of the iPhone 7 owners.