Apple has released iOS 12.3.1 for the iPhone, iPad, and iPod touch.
iOS 12.3.1 has an update fixing an issue that could prevent making or receiving VoLTE calls.
Other than that it fixes issues in Messages that could cause messages from unknown senders to appear in your conversation list even though Filter Unknown Senders is enabled.
Similarly it also an issue that could prevent the Report Junk link from appearing in Messages threads from unknown senders.
iOS 12.3.1 Compatibility
iOS 12.2 is compatible with iPhone 5s and later, iPad Air and later, and iPod touch 6th generation. See the list of compatible devices for iOS 12.2.
iOS 12.3.1 Download
iOS 12.3.1 is available for free to download via OTA (Over the Air) Settings > General > Software > Update and also you can download via iTunes.
For information on the security content of this update, please visit this website: