Use APKPure App
Get FastDormancy Toggle for i9300 old version APK for Android
Schakelt FastDormancy over "wat" Samsung-apparaten.
This app can toggle fastdormancy for i9300 using the method described in http://www.androidnz.net/2012/06/at-your-own-risk-how-to-disable-fast.html
it is only tested on Samsung Galaxy S3 (i9300).
Your device needs to be rooted for this app to work.