How can I return on Spotify premium

I Have gotten on Spotify premium, but it was wrong because I had mistake, from when I got on Spotify. I want to return this happen, that changed to use free. I couldn't find.... I sent to about this happen to on Spotify. They told me, they couldn't anything because I got from iTune. could you do me a favor? How can I return it. I want to use free for on Spotify. Plz... Could you help me? I need to help your hospitality. I don't have enough money for spend money