On Wed, 16 Apr 2014 09:12:28 +0100, nemo wrote:

Restart the phone to clear the decks.

Yep, my Galaxy SIII mini started to lie about the status of data. No
Icon, settings dialog says it's off. But if you tried to turn it on
you still got no indication. Ignored it for a day then got an
unexpected low battery warning and guess what data icon was on and I
hadn't even touched the phone...

Disable non-essential apps from automatically syncing in the background.
Turn wifi and GPS off, except when you actually need them.

And turn off data. Even if there is no traffic it still draws power
to keep the radio on.

--
Cheers
Dave.