Confused on icloud, why is it active? Not understanding why it is active on my iphone and one other system

I have a Dell Inspiron laptop where my initial iTunes started. Since then I have purchased ipad and ipad mini and my wife and I have iPhone 6s. Additionally, my itunes account is associated with 2 other desktops where I listen to music.

I just recently purchased my iPhone. All our music is under her iTunes account. Since activating my phone I have noticed my desktop (Dell XPS), both ipads, and my phone all show the cloud as required to listen to music. I don't know how that happened and I don't like it. This icloud does not work for me. If it was a repository/backup for my music but my music existed on my media as before I would be happy but now when in my car I am charged by my AT&T account when I want to listen to music from my phone or ipad where as before the music was on my phone or ipad and I just listened. How do I go back to that way of using my iTunes on my system and devices?