With the proliferation of leasing programs for smartphones from U.S. carriers, many people are able to upgrade their iPhone every year. There can be a snag, however, because all of those plans require at least 12 payments—if bought your iPhone 6 on the first day it was available, for instance, you won't make your 12th payment until sometime after September 12th, when iPhone 6s and iPhone 6s Plus goes on pre-order.
Here's how to check your AT&T Next plan for eligibility and make a payment if needed.
I'm going to approach this from the standpoint of ordering your iPhone 6s or iPhone 6s Plus starting on Apple's website, where you are given a convenient link to Get ready for preorder:
Screenshot from Apple's iPhone Site
Clicking that link opens a popup sheet:
"Make sure you're ready for pre-order" screenshot.
The top link says "Get ready now," and that's the link you want. It will open a popup window asking you to select your carrier, as shown on the next page.
Next: Choosing Your Carrier and Checking Status