Not Registered On Network (Samsung Galaxy J7—Android)

Today I tried to make a call from my cell phone to my landline. It did not work. Instead, I got, pretty quickly, this error:

Not Registered On Network

I'm using T-Mobile and my 3 other family members did not complain about their functionality so I would imagine that our accounts are just fine.

Looking for the error, I found one person who said he had the problem too and by restarting the phone it would fix his problem... for some 30 seconds.

Well... I thought I would give it a try and sure enough once I had my phone restarted I received the 5 or 6 text messages I was expecting and could again make phone calls.

This is just annoying. If you make an upgrade that requires a restart, you should give us a notification about it. I suppose it's not always easy to know whether an upgrade is going to affect the phone that much, but I've pretty much never seen anything such signal unless I had to get a new version of the kernel.