The new update is available for download on all devices. To access the update, simply download the update by going to Settings > General > Software Update. If you do not see any updates, there is no need to panic. Although iOS 12.3.1 is distributed to all devices, it may take some time to spread.
With the new update, Apple fixed some bugs in the messaging app and VoLTE calls. This update:
- Fixes issues that prevent making and receiving VoLTE calls.
- It solves the problem that messages from unknown people are seen in the conversation list even if the Filter Unknown Posts option is active.
Apple didn’t offer developers or beta versions for iOS 12.3.1 because they don’t need any feedback to make bug fixes.