In a document sent to Apple's Authorized Service Providers, Apple revealed that some customers are experiencing a bug in the iPhe 7. Some people have found that their speaker butt is dimmed during phe calls or video chats via FaceTime. It affects some iPhe 7 and iPhe 7 Plus models running iOS 11.3 or later (via MacRumors ).
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Apple recommends first to unpair or turn off devices Bluetooth cnected to your iPhe, to see if it works. If this is not the case, the service providers must run audio diagnostics. This will show if the iPhe needs to be repaired if an alert appears saying "unsupported accessory" or "device unable to detect the dock".
have been authorized by Apple to repair these devices even if they are no lger under warranty, specifically for this problem. You can schedule an appointment with an Apple Store Genius Bar or an Apple Authorized Service Provider the Apple Support page.
MacRumors says that because Apple has not yet acknowledged the bug publicly, employees may not know it or deny the informati. In this case, you can try to escalate your business to a senior AppleCare Advisor
[ Apple Releases iOS 11.3.1: Includes Security Patches and Third-Party Screen Replacement Problem Addresses for iPhe 8 ]