Cross upgrade via Apple Store APP

[Dr Kevorkian94]

I have two lines that will be upgrading to the iPhone 7. We have a total of 4 lines on AT&T and the other two are out of contract. All together we are on a mobile share plan. Obviously the apple store app is the way to go if you want to get in as fast as possible. The two lines that need upgrading are still on contract but I know I can use another lines "upgrade." I called and asked AT&T about this and they said Apple can do it no problem. However if I go to the apple store app on an iPhone we want to upgrade the only options are "Replace this iPhone" or "Buy a new iPhone." Both of these options yield Apple installment plans. If I do this on my iPad via the app AT&T next is an option. Any help is appreciated, thanks everyone!