How to un freeze sgh a707?

First, make sure the charger is not attached or plugged into the phone, gently remove the back cover and the also gently, but firmly grasp the battery and remove it, leaving the battery out for about one (1) minute. After one (1) minute, carefully replace the battery making sure it's in correctly with the metal contacts on the phone are touching the metal plates on the battery, and making sure the metal on both the phone and the battery are free from and dirt, dust and all foreign material meaning that nothing is on either set of the metal contacts, and once the battery is secure then replace the back cover and turn the power on and it should be fine. Check the settings, apps and other functions to learn why it froze, and if you can learn why then you can look into a solution so it never happens again.