If you feel lonely and ignored when nobody seems to have a solution when your software acts erratically. Take heart! It happens to novices and gurus alike. You are not a "dummy". It just takes a lot of time to get all the necessary information to pinpoint the problem.
I sent the following to Consumer Cellular after an abrupt disappearance of a long-standing annoying problem.
To avoid using up cellular data I turn cellular data on and off on my iPhone 5s. With iOS 9 it became a nuisance because the settings would not change quickly, often it could take two minutes. This doesn’t happen on my wife’s iPhone 5c with iOS 8.
I thought the problem could be iOS 9.1. The problem did go away when I installed iOS 9.2. Then the problem came back.
Yesterday, we changed our data and voice plans, splitting our account into two accounts.
Today, I can turn cellular data on and off quickly. No change in iOS. No change in other settings.
Could it be something Consumer Cellular or AT&T is doing?
This also makes me wonder it I changed my bank prematurely. Would
Consumer Cellular now let Republic Banks software operate smoothly? Nope, it still gives system error after I enter my password.
Anybody in CC have the time to really look into this? Have any other users reported a similar problem.
Note added 2016-01-18:
For one solution, see http://magree.blogspot.com/2016/01/more-on-erratic-iphone-cellular-setting.html.