I am currently using an unlocked 6 plus that i purchased from apple (tmobile version). I'm using it on att. I went into att and got a sim when I bought it. they handed it over for free and i put it in and that was that. I ordered a new 6 plus (different color and more gb) that is arriving soon. Should i activate it with the sim it already has in it or should i take the sim out of my current 6 plus and put it in the new 6 plus?