Unlocked s21 Ultra showing as "Unknown Device" and not supporting 5G or Extended Range LTE on My Mobile account

Exactly the same issue here with the two S21 Ultras we bought directly from Samsung. I have spent countless hours of the phone with all levels of their tech support. Each time I've been told at the end of the VERY long call that 1) they had figured out what the issue was, 2) had submitted the necessary hoodoo to get it fixed, 3) they asked me to be patient and give it 48 to 72 hours for the changes to show in my account, and 4) that they would call be back on a specific date to make sure everything was fixed.

Not one time has anyone called me back. None of the 'fixes' ever happened.

I'm beyond furious about this, most of all because I feel like I've been fed a ration of crapola on every call. It's ridiculous and disrespectful.

I am extremely unhappy about this, and after years as a faithful customer who has consistently over the years promoted T-Mobile to friends and family, I no longer feel that way.