Update to Android 4.4 also enables support for Sprint MVNO Zact Mobile
Per this internal document, the update should be available starting February 13 and will also enable support for Sprint MVNO Zact Mobile. You'll need to make sure you're on the current build of the software and have everything stock and proper to get this one. Hit the forums if you need any help there.
We hope this pans out, and Sprint Galaxy S4 users have an extra-happy Valentine's Day.