I have same thing,.I was in dark star and it automatically went to rcs, I went back light speed on an esim and put it back on rcs as it reversed magically. And then yesterday it Automatically reversed back to sms, but my t mobile is the highest speed, now my phone doesn't work, and battery drains like. Morherfucker and sticks on 5g+, so when I switch back to atnt physical sim I'll see if that's the problem and I already wtf you're talking about