This is a widely known issue with the iPhone 7/7 Plus models, it has to do with the Audio IC which is a chip on the internal logic board that is prone to failure.
The only “fix” would be an experienced technician successfully jumping a pin on the chip using specialized micro-soldering workbench tools. This is not an issue you can throw parts at to repair.
Apple will not acknowledge the issue, but they will treat it as a whole-unit replacement when you bring the device to them. If you have AppleCare+ coverage on your device, you are covered.
I would not take this to a repair shop unless you absolutely trust the technician working on it. One slip-up during a job like this can render the phone completely useless as the tech can break plenty of other fragile components on the board if they are not careful. One workaround to the problem is using bluetooth headphones, if you do not want to spend the money to fix it.
I’ve been talking to Apple Support and they have confirmed this is a software issue (after running diagnostics there’s no hardware problem; with my phone at least). Waiting for Apple to confirm what they propose doing to fix the issue but they have been slow, 11 days and counting. Initially they said I have to buy a new phone!!! For something that is not my fault, rather poor customer service ... This issue occurred with iOS 11.3 as well and seems to only affect certain iPhone 7 models, other models work fine. Odd thing is that 11.3 worked fine on my phone, but 12.1 does not. Also Apple to not offer the option to downgrade to 12.0 that worked perfectly fine on my device. Very frustrating :-/
Marcus Kittel さんによる
Hi I have the same problem have you had any more news from apple?
I took my phone to apple and they refuse to admit it’s their fault. They kept insisting I dropped my phone and that the update just triggered the issue that was already there. Nothing surprising from apple. I can’t believe they get away with ripping people off this much
Same problem after update. I went to Apple store today and they said I have to pay $350 for a replacement phone. Such poor service. They claim it's a hardware issue but clearly if it happens after an update then it's a software issue.
CASTLE EXPRESS Moving さんによる
i figured it out just now..don't spend money. it is a software problem.. download ios software from your itunes in pc . then restore it. but before you restore just backup any thing important files from your cp.. hope this help to you..