Prevent & disable iPhone iOS 9.2 from forced/ pushed auto downloading updates?
The closest I came was preventing all my iOS devices from reaching the update server. This envolves configuring your internet router in order to do so.

Configure your router to block the following domain: mesu.apple.com

Doing so will still allow your iDevice to talk to the Apple Store, allowing you to download/update iOS Apps.

Some routers (like mine) only allow me to block 'web sites' not domains. Luckily, that is all we need to do. Blocking https://mesu.apple.com also does the trick.

I would say blocking the whole domain is a cleaner solution if possible however.