I upgraded to 8.0.1 and then backtracked to 8.0. Since then, my VolLTE setting isn't working. I got a message saying it was disabled by my carrier and I can't turn it back on (Under Settings-Cellular-LTE-Voice & Data). I had it enabled in the morning and it was working and now it's not since the upgrade/downgrade. I am with Verizon. Since it's a business account, I cannot directly call Verizon and add features, so figured I would see if anyone else was having issues.