I can't lock my screen. I can put it to sleep/black but it will go on in my pocket and call random people. When i go to settings/security&privacy/screen security. When i turn on "power button instantly locks" and leave the setup menu it will go back to being off. Is there anything i can do to make it stay on? I already have made pattern but when i push the power button itll send me straight to the menu. Miui version: 3.1.11 Phone: samsung galaxy s 2 Thanks in advance!