Planning to buy a 6S. I live in California with AT&T as my service provider. In 6 months, I will be on vacation in South Africa. I want to be able to buy a SIM card, so it seems that buying the 6S unlocked is the way to go. What are my choices for buying an unlocked phone? Google search isn't very clear about this. I know I can buy the 6S unlocked from the Apple Online Store. Probably what I'm going to do. Does AT&T sell unlocked iPhones directly?