Wow this is confusing, so many of us in different variants and conditions. We are on Family Plan AND Unlimited Grandfathered, AND we got Next about two years ago. When we got Next they tried to tell us to give up Unlimited and my husband told them absolutely not. They still gave us Next and I gave them my beloved IPhone 4 for a $100 off my iPhone 5s. (Big regrets about that, I loved that phone).
We upgraded me to iPhone 6 last fall but I never turned in my iPhone 5s. We paid the 5s off and gave it to my daughter.
We had to order on AT&T site last year and it was a disaster. Apparently during the first few minutes that orders came in they had a problem and ended up writing orders on Post-It notes or something. Those who were first in the queue ended up among the last to get their iPhones. There was a huge thread of us on the forum cheering each other on every time somebody finally ended up leaving processing limbo.
I'm not sure how AT&T will let me place my next order.