I'm using an unlocked Samsung Galaxy S5 AT&T (model: G900A). It's currently running on version G900AUCUcBOC4 (released 4/2015). After April, AT&T released two new softwares: G900AUCU4BOF2 and recently G900AUCU4BOF3 (more details: since I cannot post link, you can search for this page on google...