Most of these codes and more are listed in the Carrier Specific area of the Settings app. In settings, tap Phone, then go down to the Carrier Preferences. (Mine says "AT&T Services") Once there, you can find how to check balance, pay your bill, view data&msg info, or view minutes. The first one in the article is incorrect, however. The correct AT&T code to find upgrade eligibility is *639#. This is *NEW# - which is much easier to remember.