Call Failure with IOS 12.3.1

I have a passion and hobby to go through complete literature and review of all iOS releases and needless to say I haven't missed iOS 12.1.3, 12.1.4 12.2, 12.3 & 12.3.1 assessment published on various news media and on Apple web page including leading news magazines (Forbes & Fortune Magazines).

The major takeaways from this iOS 12.3 update is Apple TV, Kids TV, The app is available on Samsung TVs, tvOS has been updated, AirPlay 2, Apple TV app,

And iOS 12.3.1 includes bug fixes for your iPhone and iPad. This update:

• 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
• 
  

No where I could find any link on the problem of "Call Failure & SMS Message" faced by you. Introspect and have a complete and thorough check on the way you handle settings on your iPhone.

Read often for a peaceful life.

Solution.

For You: If you can't make or receive calls on your iPhone - Apple Support

For you Co-Worker: About iMessage and SMS/MMS - Apple Support

I have 12.3.1 and I can assure you that even with "Filter Unknown Senders" turned on no messages ever go to the "Unknown Senders" list. I have spent hours going through everything. and no banana.

I have been an IT profession since 1967. US Navy Polaris submarine and 30 Years in AT&T as an IT professional so don't preach to me about going through everything. If you have a set of IOS settings that are necessary to make this work I would be thrilled to know.