Watch your bill if you buy an iPhone 6S from Apple!
I have (well...had) a plan with two phones. One was an iPhone 5S and the other was my father's basic cell (that couldn't used data if it tried). I ordered an iPhone 6S Plus from Apple and replaced the 5S on my account. Or at least I thought I did. For some reason AT&T decided that these should be treated as separate so I am now getting charged for two data plans and two phones (instead of one data plan with two phones).
Watch your bills, everyone. There are shenanigans afoot.