Update for the community, for those who came over from AT&T with their unlocked devices.
Just got off a call with T-Mobile Tech Support, and nice enough guy but the message back is we are all screwed if we were hoping for any software updates (or security patches?) from T-Mobile. Best as I can tell T-Mobile (only?) pushes patches and updates to any device on their network with their firmware number only.
Again, nice enough Tech Support but ... its 2017 and while patching / updating software is not trivial, its also not impossible to do better today. You'd think there'd be a smarter way to deal with this backend process, considering every phone has a unique ID!
Just wanted to share with the community ... heads up, and if anyone does find a way to get their updates someway / somehow please let us know. Thanks ...
You are correct in that you will not get the updates OTA via T-Mobile. Even though it appears that T-Mobile is sending the update it is actually still coming from Samsung's servers, just the OTA notification is only looking for the TMO model number when the phone is on their network which of course yours isn't a TMO model number.
There is still a way for you to get updates however and that is to use Samsung Smart Switch. If AT&T has released an update it will be available for your device via smart switch.
While the devices appear the same there are sometimes small differences in the firmware because of network capabilities and TMO devices especially have to have a lot of extra firmware since they have the most advanced network out there. So the radio for one but also things like wi-fi calling, RCS messaging, GoGo inflight messaging, etc all have to be incorporated at an OS level which is why each carrier has it's own slightly different version of the OS and updates come out on completely different schedules because Samsung has to program them each individually.
There is a way but it is not sanctioned or supported by TMO not to mention if you mess it up it bricks your phone but using software called ODIN and some searching/research on XDA Developers and you can find the software files needed to essentially convert your device from an AT&T version to TMO version but as I previously said if something goes wrong..........
Stevetjr - awesome.
That's more than an acceptable answer for me as a customer. Already have the Samsung Smart Switch software and it is a handy set of bits for anyone with a Samsung phone. Would just have been less stressful if T-Mobile published the (alternate) process somewhere. I'm sure customers moving to T-Mobile would understand and appreciate that they can really BYOD in terms we can understand.
Again awesome response ... many, many thanks ...