Dear <insert deity of your choice>, all of the advice on this thread is terrible.
From my experience as a tutor, here's what I'd recommend:
1. Don't "confront" individual students about being on their cellphones or not paying attention. It's their loss for services that they directly/indirectly paid for, and if you do go ahead and do that, can make you look like a total rear-retentive person since I doubt that their actions are that disruptive.
2. If a student is being disruptive (from my experience this usually can be someone who ends up asking a billion questions), just redirect other kids in the class to answer his/her question first before answering it yourself. Saves you time and trouble, and keeps the others engaged. Additionally, you can also ask them come talk to you after class if their questioning is holding back your lessons/review/whatever. Now, if a student is being really "disruptive", which I honestly doubt they would be, it would be a good idea to talk to them 1-on-1 about it later.
3. Perhaps your students are not paying attention because your material is too easy or something that they're familiar with? Try changing up your lesson plans, and maybe try including some interesting activities like group competitions to keep their attention.