I'm not sure if this is something on Samsung's side or not, but I found band 12 LTE slower than almost any other form or interest access. I can even play music when using it. Which $ucks, because we don't get much band 2 or 4 in our area.
I've disabled band 12 only to find out there is no signal most if the time without it, so it's not the phone switching to it when it isn't needed.
