From the TMobile website
Beginning May 23, the Samsung Galaxy S 5 will have a software update to Android version 6.0.1/ Baseband G900T3UVU1GPE1 OR G900TUVU1GPE1 via Wi-Fi or Samsung Smart Switch for PC. This update provides new features.
Meanwhile I've got a defective expired lollipop...
I must say that TMobile while its network sucks, they at least keep their customers notified rather well telling its customers when software is in testing versus VZW who doesn't tell it's customers anything.