Androidnewb I don't know what VoLTE disable override is (Android AND phone newb here :) ), or where to configure it.
I only mentioned that because you mentioned changing other overrides, so I was just saying: If settings are still changed from the default, that could cause issues.
VoLTE is in the same area as these that you mentioned:
Disabled/enabled Vo5G
Disabled/enabled Wi-Fi calling (Wi-Fi works as expected)
You can find them over at:
Settings > network & internet > SIMs > [Tmobile or maybe a different name] > carrier settings overrides
Here it'll say Default: available for various settings which means it should be enabled. You can force disable or force enable things which might not make a difference. Changing these won't change anything I think in your case unless yours are different than mine:
https://imgur.com/a/apogQvF
Your settings could be different from me depend on our area, maybe you have more 5G around you.
As de0u mentioned
do you have another phone to test your SIM card in momentarily? Call a business or something real quick. A family member or friend's phone works too.
If not at the moment, you could still turn off the phone and remove your SIM card and put it back in--double checking it's in the slot correctly.
While it's out, you can clean the gold colors pads on the SIM card.
Cleaning the SIM
3 options, choose 1:
Turn off the phone, take out the sim card and clean it with a Q tip and a bit of isopropyl alcohol.
clean it lightly, rubbing with a pencil eraser.
If you don't have any of those, you can use your finger, just make sure to touch this spot labeled ground first and no other spot on accident. Touch the ground spot for 2 seconds.
image of a sim card
After touching that spot for 2 seconds, you can then rub your finger on all of the brass colored contacts. Try to not get it wet with your finger. Dry it with some cotton if you have it.
See if it works now.
Let me know if it works in another phone or anything else you find out.