Apple dropped iOS 12.3.1 today with bug fixes for VoLTE and the Messages app.
iOS 12.3.1 Notes
- Fixes an issue that could prevent making or receiving VoLTE calls
- Fixes issues in Messages that could cause messages from unknown senders to appear in your conversation list even though Filter Unknown Senders is enabled
- Fixes an issue that could prevent the Report Junk link from appearing in Messages threads from unknown senders
It’s a bug fixing release so that’s why it’s fast on the heels of iOS 12.3, which was released earlier this month. In that release we saw the redesigned TV app, Apple Pay for iTunes and App Store purchases, new types of Express Transit options, and more.