Pynthexsia Unified allows you to unlock all Premium features of Spotify for free. To use this tool, you have to be jailbroken. iOS 6.0 - 9.x are supported :)
Spotify released Version 2.5.0 in Early 2015 and that version was the first to patch Pynthexsia Unified 1.3 which was used to crack Spotify 1.8.0 - 2.4.0. Shortly after that, Spotify CS, a modified and signed version of Spotify 2.4.0, was released to keep the functionality of Pynthexsia for people who didn´t have the chance to download Version 2.4.0 before its end.
After months of working, the final version of Pynthexsia Unified for iOS 9 was released, with Support for Spotify 4.6.0 and (hopefully) higher :)
Pynthexsia Unified (2.1.2) still works, tried with Spotify 5.7.0.