This guide is to help you understand the way to block (and also unblock) someone through iMessage on a Mac, iPhone or iPad. Before the introduction of iOS 7, blocking an individual phone number was something that the Apple operating system did not allow you to do. To unblock system preference delete the file then add.app then put in Slcache, SlSto. So this is my first video on this channel.This is for school laptops. To unblock system preference delete.