Apple finally addresses microphone issues for iPhone 7 and iPhone 7 plus

Apple has confirmed that there are microphone problems on iPhone 7 and iPhone 7 Plus running IOS 11.3 or later. Users see a grayed out speaker button during the call. This prevents customers from being heard on phone calls and face time video chats. Moreover, some users reported about malfunctioning of Siri in the latest iOS update.

What Apple said:

Apple has not publicly discussed this bug related issue. Instead, it has internally instructed Apple Authorised Service Providers by an internal document obtained by MacRumors.
Apple, in the document, has instructed service providers to ask users to disconnect Bluetooth headsets. If this doesn’t fix the issue then users should run audio diagnostic. If the diagnostic either mentions ‘could not detect dock’ or something similar to it then the service provider will repair the phone. However, Apple has not discussed about the cause of this issue in that document.
The affected devices which do not have warranty may be an exception. If the users feel his/her device is affected, then he should make an appointment at an Apple authorized service provider or Apple Store.

This bug is only affecting iPhone 7 and I Phone 7 plus running on  IOS 11.3 or later. Apple authorized service providers will repair the phone free of cost except for the ones without warranty.