Asus FonePad or any phone for that matter.
Steps:
1. Download Astro File Manager from Google Playstore
2. Open the "System" file
3. Then the "App" file
4. At "View Settings", tick "Show Hidden Files"
5. Phone app appears!
6. Go to Home screen. Click on [six dots in circle] for apps.
7. Search for Phone app. Long-press and drag it to the Home screen.
Good luck!