I currently have AT&T and I want to get the iPhone 5s. I have an upgrade, but that might not have anything to do with my question. So I was wondering if I can buy the iPhone 5s and take the sim card from my iPhone 4 and put it in the 5s? If I can do this that would be great. If not then I'll have to figure something else out I guess lol. Ok so thanks for your answers