Convince my mom to let me go to a concert...?

Your mom was just not saying that to make you cry and tick you off. Trust me. I know it seems like that now and it seemed like that to me too when I was younger, but it's really not the case. Your mom is probably just worried about you. Which is basically the reason moms do most of the stuff they do. Just explain to her how badly you want to go, the money and stuff that was already put into going, and that even though you love God and are a religious person you would just much rather be at the PATD concert.