After the models sold by Verizon and Sprint both started getting the Lollipop update earlier this month, it's now time for T-Mobile's iteration of Samsung's Galaxy S5 to receive the same treatment. In a bit of good news for owners of the S5 who bought theirs from T-Mobile, the carrier has started rolling out the update to Android 5.0 for this device today. The update is available over-the-air, and as you can see the download necessary to perform it is over 900MB, so it might take a while to finish. As always in these cases, your phone will notify you once the new software is ready to be downloaded and installed. If that hasn't happened yet, you can always force it to manually check using the Settings menu, though whether this will actually successfully bring you the update isn't clear. Alternatively, you can use Samsung's Kies desktop software to get your Galaxy S5 its first taste of Lollipop. After applying the update, you should be on Android 5.0, build number G900TUVU1DOB1. Source 1 Source...
Source: http://www.gsmarena.com/samsung_galaxy_s5_now_receiving_lollipop_update_on_tmobile-news-11241.php