s3axel, when you have the time, I would love to test a 1.0.5BA build for you :)
Well, as long as you have the original, unmodified recovery available you can always try to flash the existing modified 10.0.3 recovery... If it doesn't work just go back to fastboot and re-flash the original recovery again...
I'll update OP th...
Your device would have to be compatible with your carrier.
I have dual sim, so 2 carriers. Only 1 is supported for VoLTE. Not much you can do about it except ask your carrier.
Do you have a unlocked model or some carrier brand? Remember the Sim tray is double sided.
But.. I want a 1100 dollar device with EVERYTHING.. I picked a OnePlus phone because of software, not price.