On the heels of publishing iOS 12.3 earlier this month that brought some major changes as an updated TV app, Apple has just released version 12.3.1 of its mobile OS which mostly contains some corrections to correct bugs related to iMessage as well as
Solves an issue that can prevent you from receiving or receiving VoLTE calls
If you want to update your device to iOS 12.3 now, you can do so by navigating to Settings > General > Software update on your device and pressing at "Download and install" at the bottom of the page. You can also use the update via iTunes by connecting your iOS device to a computer.
After the conference we can then be in the store for an iOS 12.4 release possibly later this summer, since version 13 would probably be out in the fall along with the release of new iPhone models.