I have the same issue. A friend had a T-Mobile update on November 3rd or 4th, 2019 and all of sudden the texts started coming through to my phone as little boxes or with no content at all. The person is receiving my messages though. I have an older LG phone, but am not having issues with texts from anyone else - just the T-Mobile user. I am looking for how to fix this as well. I saw something about an app for T-Mobile users to change such messages to "plain text", but have no further information.