How do I revert to iOS 12.5.2 on my iPhone 6? This is a safety issue! Upon upgrading to iOS 12.5.3, my microphones quit working, which means that I effectively cannot make calls on the phone.

The microphones on both of my iPhone 6 devices worked fine until I installed the iOS 12.5.3 update. After the update, the microphones were no longer working on either iPhone 6. Without microphones, the devices are no longer telephones capable of making emergency calls. As a result, the software glitches in iOS 12.5.3, which broke the microphones, are a safety hazard. When will Apple fix this?

This reply made me realize that the problem I was experiencing was most likely due to an incompatibility between iOS 12.5.3 and one of my user settings. That is, both of my iPhone 6's have very similar user settings; however, this gentleman's iPhone 6 probably has very different user settings.

On that assumption, I tried "Reset All Settings" on both of my iPhone 6's. That reset fixed the microphone problem on both phones, and the microphones are now working again on both phones.

The question remains, which of my iPhone 6 user settings were the culprit(s) in being incompatible with iOS 12.5.3 and thereby causing the microphones to quit working? Apple developers probably have a good notion of which user settings those are. The responsible thing for Apple to do would be to post that information, so that all users could easily fix the microphones on their phones after any iOS update. (There are many other posts throughout this community about microphones no longer working after an iOS update.)

Ideally, in the future, Apple developers would take better care to not incorporate changes in any iOS update, which could be incompatible with any user setting thereby resulting in critical failures. Failure of microphones to work is critical, due to their vital function allowing the device to be used as a phone and therefore their vital function in protecting user safety and security.