Well that is incredibly odd! If this is specific to certain locations, the issue is definitely related to the network. Have you had a chance to reach out to our over the phone support folks yet? They will be able to create network trouble tickets for these locations to have them investigated.
Every body here make the same complaints about reception with Apple products. Appear LTE but no internet connection, since 2018 I trade 3 equipment and still the same problems. This time I call costumer service and told me take my iPhone 11 pro max to warranty, later make a complaint with the insurance, but my all phone are new and have the same problem no internet connection is sad because I love TMOBILE. I week ago I buy Samsung Galaxy and my problems resolved I have internet and I received all calls. The problem is apple products on Tmobile network The speed test is from my new Samsung Galaxy I need to buy because I need proof is the network no the equipment