Spotify uses mobile data even when disabled in root settings iPhone

[dee2may]

After a recent update I found out that spotify is using mobile data without my permission. I have disabled the mobile data usage of spotify in the root settings of my iPhone, yet it still seems to "go online" when I don't have access to wifi. Before the update I could be certain that spotify would only play from my offline (downloaded) playlists (for example: the search function would not work), but this is not the case anymore. I think it's a hassle that I have to manually select the offline mode each time I'm on the road! No mobile data acces should mean 0 4G for Spotify right? Is there some kind of bug in the latest version?
Any help is appreciated! Thx Anouk