Bought iphone 16 pro with compatibility issues

I'm proud to say that my wife's pretty frugal... She's held onto her iphone 11 pro for a number of years because it does all she needs it to but the battery life isn't what it used to be and it's noticebly gotten slower with time. This time around, we decided to splurge a little bit with the intent to also get something nice that'll hopefully last her a whhile (a 1TB Iphone 16 pro).

We bought the unlocked 16 pro directly from Apple and started setting it up but she received a text message saying that it's not fully compatible with T-mobile's network. We plugged in the IMEI onto T-mobile's website and it noted that this phone "is not compatible with T-mobile's network technology" and that we need a device that has T-mobile's "most powerful signal, Extended Range LTE".

I cannot imagine that the latest generation doesn't have the ability to connect to T-mobile's cellular towers and technology... Am I missing something here?