Hi there friend, hope you're well and sorry to hear of this issue with connectivity.
You may need to reach out to T-Mobile for this issue as it sounds like a carrier specific issue.
Some routine troubleshooting may help here:
If one of these steps above help, let us know here and select this post as the solution.
That has been my solution as well was to go switch off 5G and only use LTE/3G/2G. It was annoying to have my phone just stop working without any warning. Re-booting was the only way to get it to work again. Will wait for the next software update before I try 5G again.