I actually found that shouting never worked, I spoke once in a reasonable voice, if it didn't get done, I took away something they valued. No shouting or yelling, I just walked into their room and took it and locked it away in the cupboard eg a favorite shirt or shoes and if really necessary their charger cables. Then I just did what I had asked them to do myself. To earn back their confiscated item, they would need to apologize and do chores. If they decided to try and get into a screaming match, I just ignored them and continued what I was doing, it's not easy and you need to learn patience, lots of it. If by the end of 10 days, the item hadn't been earned back, I gave it to charity or threw it away, while there was a confiscated item in the cupboard, no money was given for anything they needed, not for school, not for outings with friends, etc, they soon learned. Good luck