A Samsung phone with the model name SGH-I337 just passed its U.S. FCC tests with flying colors. It also includes AT&T 4G LTE Radio Bands. For the most part it's obvious it is the new Samsung Galaxy S IV for AT&T even though it doesn't follow their usual naming convention. It hasn't been officially confirmed to be the SGS4, but the timing is extraordinarily coincidental for it not to be. Furthermore, earlier rumors pegged the AT&T model name as the SGH-I337. We should know in just a few weeks.

Source: FCC