iPhone network problem

Hi

I sporadically experienced network problems with my iPhone 5S 16GB for quite some time.

Out of the blue the network is gone despite good coverage.

The only solution was to reboot my phone, being forced to type my passwords again in some apps. The airplane mode did not work.

Of course I have installed the latest iOS 8 update - it also happened with an earlier system.

And, if I am not mistaken, also on my former iPhone 4S...

I wouldn't bother too much if I have to switch off my phone here and then to solve that problem.

What really is a big issue for me is the suddenly disappeared network connection - without me noticing it!

A kind of alarm, notification etc. would be some kind of compromise, at least temporarily...

I am aware of that also other people experienced the same phenomenon.

I already checked the related sources online and could not find a solution that addresses that issue.

As a medical professional in the outskirts of Norway I am depending on the reliability of my network connection.

It already happened that I got an important call and could not be reached due to missing network connection. Worst of all - I did not know/notice that.

Very inconvenient to have to check the phone all the time in case that might have happened again.

I even might be forced to get another phone, a thought I do not like very much.

On the Apple support pages no help at all except the obsolete tip of switching off...

Hello Apple?

Anybody?

Thanks in advance!