Seems to be a Samsung issue. I have had issues with my unlocked Note 10 plus since I got it. I have had 2 sim cards. Sprint blames Release from Samsung. Sprint got bought out by Tmobile boo. Now my service is worse than ever. No signal. I am supposed to stay on my own wifi and wifi calling to be able to use my phone. When I travel my calls drop people can't hear me it's awful. The worst it's like going back in time. My note 4 works better.
I am on my 3rd SM-N976U phone now that cannot get data/internet over cellular on the T-Mobile network. New 5g sim card installed at the T-Mo store, I have spent hours on the phone with T-Mo support, tried every setting imaginable, reset everything including the dreaded factory data reset.
Here is what I have discovered so far:
With the most recent (my 3rd) Samsung Galaxy Note 10 + 5G phone, the first thing I tested after taking the phone out of the box, putting my new 5G sim card in and turning on was to see if it was getting data/internet over the cellular connection and it was. Great, so I installed all my apps, cellular data still working, great. Next came the T-Mobile OTA software update Baseband N976USQS4CTK3 after which data/internet no longer worked over cellular. Strangely enough the phone works perfectly in Mexico on the Telcel network, data works fine over cellular in Mexico. According to the T-Mobile expert there have been numerous problems with the new 5G network and Samsung phones and they (T-Mobile and Samsung) have been working together on software fixes but as of today 01.27.21 my expensive Samsung phone will still not get data/internet over a cellular connection on the T-Mobile network.
My 4th Samsung replacement phone is being shipped today, when I get it I will try for as long as possible to prevent the T-Mobile OTA update from installing so that I may have a usable smart phone until Samsung and T-Mobile figure out how to fix their mess.
I have no problems on my S5, Note 8 or Note 9 with my new sim card or the old one before they changed it.