Hi! I'm on the verge of purchasing my iphone, but want to understand unlocked vs. locked. If I buy an unlocked phone on Ebay (not from an ATT store), what's the next step in order to get service? Do I still pay the $20/month if I'm an ATT customer now? I am an international flight attendant, and don't want to pay the standard ATT long distance fees. So, basically, how do I get service once I have the phone? Please help me!