iPhone 5S can't find IOS 8.4

Hello,

My iPhone 5S can't find any new update. It is currently running IOS 8.3 (12F61).

There is a notification at my settings icon on software update, but when I head over to software update it says ' IOS 8.3, Software is up to date '.

When I connect the iPhone to my computer it says IOS 8.3 is the latest version for my iPhone, while my iPad and other devices are on IOS 8.4.

Thanks,