Tell them you are an athiest and you do not agree with the beliefs of Mormonism. Share your ideas of you just believing in what you want to believe. If they punish you, say that they are forcing their beliefs onto you, and that you have a human right to believe in what you what you want and you don't have to follow the religion. You probably will still have to go to church each Sunday, but just ignore it, but hope you'll be able to have a Girlfriend before 18. If that fails, or you want an alternative, get a good education, and play along with the religion. Once your 18, make some money, GTFO and move away, and live your own life. I may be Christain, but I know you don't want to be one, and I respect that and I won't harass you.