Samsung A33 5G and A34 5G only connecting to Edge

Hi. My partner and I recently moved to the US from Hong Kong, where we had purchased our unlocked Samsung Galaxy A33 5G and A34 5G phones. In the US, we have subscribed to a T-Mobile 5G plan, and had checked the device IMEI's beforehand on the T-Mobile website, which says both devices are fully supported on the T-Mobile network. Both devices, however, are unable to connect to 3G/4G/5G data, and can only connect on Edge. I've tried resetting the connection settings on both devices, and have checked the APNs to make sure they have the correct details (they do). I have also made sure both phones have been updated to the latest Samsung software, and have tried restarting multiple times whenever I've made a change to the settings.

I am genuinely perplexed as to why these fully unlocked phones which T-Mobile says are supported are unable to connect to the 3G/4G/5G networks. We went back to the T-Mobile store where we bought the SIMs/plan, and their only advice was to buy new unlocked phones.

Does anyone have any other ideas before I spend a bunch of money on what seems like should be a solvable problem?