iTunes Overcharges

iTunes has been over charging me for a while now. I have the Suga crush candy Saga game & everytime I’ve paid for something in the game tht cost one price I get double charged. For instance I just paid for a package tht cost $9.99 & iTunes charged me $21.97 for it. And it always does this to me. There has got to be a glitch in your charging system somewhere. I need to know how are you going to fix this problem tht has been happening to me since I downloaded the game. I’ve been getting ripped off by ITunes & I’m not at all happy about it.