I have a Samsung Galaxy S8+ (SM-G955U) that I ported over ti T-Mobile.
I had to enter download mode a few times in order to get the "rebranding" pop up where my phone knew it was from another service provider and uninstall the old one.
Now my phone is Branded as T-Mobile all over. I then factory reset so I can start from fresh.
I was stuck on Band 4 though. To get access to Band 12, and to turn off all the other non-needed bands, I opened my Phone app and dialed this:
I then went into all the options and only kept the (*) next to everything that T-Mobile. So I unchoose all options from WCDMA & TDSCDMA, then only choose 850 & 1900 in GSM, and bands 2, 4, 5, 12 & 66 in LTE.
This should now allow your Galaxy S8 / S8+ to connect to Band 12, and stop connecting to only Band 4.
I then couldn't access my Media Settings. On my line it just says: "This line does not have any eligible media settings". So I had to call in and they just added 3,000+ days of HD Streaming Day Passes which enabled the service. You can check this by using SpeedTest to verify actual throughput, then using Fast.com to verify Netflix throughput. If Fast isn't showing near the speeds as SpeedTest: your HD Streaming is disabled and needs to be enabled. Mine is now enabled and both speed tests get similar results.
Finally, since I have ONE Plus, i wanted to enable Name ID and Voicemail to Text.
However, these are the only 2 network functions provided by T-Mobile that I can't seem to enable still.
When I try to enable Name ID, it just keeps saying this:
" You do not have permissions to change services to this line. To add NAME ID from your device and to protect you from unauthorized charges, you will need to update the Primary Account Holder settings. "
My line is the Primary Account Holder line, it shows up in all systems as the PAH / ACH and I tried this using both Wifi & cellular on all 5 bands I mentioned earlier. So I don't know what to do with this.
Then, lastly, for Voicemail to Text, it shows me the page saying that I need to purchase the feature, which is odd but I pressed Confirm anyway, but then it just says:
" We are unable to update your account settings at this
time. Please visit my.t-mobile.com or call 611 "
So, now I'm asking here for help.