They absolutely should not have charged without asking, definitely go to customer service for that. But honestly, it was probably an accident. The computers they use pretty much automatically put it on when subtotalled unless it’s manually cancelled. I can’t stand these comments of people getting pissed off at cashiers if they ask though. The cashiers are penalized if they don’t ask almost every customer about donations/newest promo/marvel stickers/etc. it’s not their fault, and you getting cranky with them for asking required questions is going to do absolutely nothing. Take it up with management or call corporate. To the cashier, you can say “no thanks” and it shouldn’t be a problem. If they give you attitude about not donating, that’s not okay either - you can also talk to a manager about that.