My 7 will be arriving tomorrow and I want to use my line instead of the other line on my plan it was upgraded with. Do I pop my 6S sim in before I turn it on and go from there OR do I activate it as is (with the other line) and then switch the sims? The other line was upgraded with The next program. An AT&T rep told he to just switch the sims but never told me when to do it. Any help is appreciated, thanks everyone!