Q: I clicked on an app that I thought was free and it isn't. How do I stop it so that I don't get charged?

I clicked on an app that I thought was free and it isn't (I thought I was downloading Hello Hello Spanish and instead it was Hello Hello World). How do I stop if from downloading so that I don't get charged? I've highlighted it and clicked "remove" but it keeps downloading. I do not want my school charged for this app which I didn't want! Help!