1.Hid app icon on the desktop, so your kid cannot find the app to delete.
2.Enter guardian number.
4.Now you can gave your set phone to your kid to use.
5.Use the another phone with guardian number which set at the 2 step, call the set (kid) phone.
6.If your kid decline your calling, it will be locked, can't do anything except to call you back!!!
But now, because this is free version, not only call guardian number can unlock phone, but also review can unlock too,So if you confirm it is useful for you, please buy it.The address is https://play.google.com/store/apps/details?id=com.dobi.ignorenolongerpay