I9506 unlock drop calls

My problem: I9506 S4 lte+ t-mobile austria, root 4.2.2, unlock ok with z3x samsung tool 17.3. Update to 4.3 and insert orange romania sim (new micro from orange) and calls drops very often with network registration failed. i tried restore old nvm, all 4.3 roms from z3x support, nothing happend. please help, my client said is my fault cause with t-mobile sim works best.