In this fight, you loose. Entertainment machina is 24 hours there, millions of other adults engage to keep your child staring at the screen.
What you can d is being an example. Show your child you're not addicted to it. Show that it's not so important. Your child will get the phone someday and it will take you child's attention. But there inside your child will have the feeling, the understanding that it's not really important. Because you were a good example.