"Restrict background data" keeps turning off after a while I have Android 6.0.1, original Samsung version on my Galaxy S5 Neo. Since I'm not on any mobile data plan and have to pay every MB I use, I'd like to restrict background data - once and forever! However, it keeps turning itself off after a while. (I don't know after what time - I often only notice it a few hours later.) So quite often, I don't notice that it's disabled again, then go online, and tons of stuff are downloaded, every single bit of which I have to pay...

What might be the cause of this? (It's not rebooting - it happens without any reboots in between.) How can I make sure background data is simply always disabled?

(I know there are some firewall apps that might help, but they either need the phone to be rooted, or they route your data through some VPN. I don't like either solution.)
I have the same problem but I know what causes it. When I display current active tasks I accidentally touch "Background data restricted" which causes it to be cancelled - but I don't notice I have done it at the time.