Unauthorized charges to my account

My account is illegally charged by Tiny Tower (Nimblebit LLC) for Tower Bux, for Bloon TD5 by Kaiparasoft Ltd., Contract Killer 2 by Glu Games Inc., Big Win Soccer and Big Win Football for Stacks/Piles of Big Bucks by Hothead Games. All in the past 3 weeks. How can I cancel those an get a refund to my account?