That the carrier controls. It's rarely a Samsung thing. Back to the carrier counter to ask them to try it, fix it. If you need to go off the reservation, find XDA forums.
I've been trying to update my S5 (G900A) to the latest OS, but whenever I go to software update and I check for updates it comes back and says the current version is up to date, even though I am on Android version 4.4.2, the phone is also not rooted so it should be able to receive updates. Does anyone know why this is happening and how I can update to the latest version of android?