charging for extra plastic bags

went to k90 towers this morning at 09h18. i bought 5 small items and asked the cashier Vanessa Speelman for ONE Plastic Bag, she scanned two bags, this i noticed as she returned the other one as the packer told her one was enough, but she already charged me but had no nerve to tell me, as i look on my slip i see i have paid for 2 plastic bags so i went back to her and asked her about it to which she just acted suprised and i showed her the sleep, and common sense would also tell her who would buy two bags for those things?? and i asked for ONE Bag myself,i accept errors are made but you dont hide your errors from me especially if im paying for your errors!!it doesnt matter if its cents but its my money and i need to know about it, just know this could be a mistake or it could be a **** to rob your customers, look at thisR0,46x 100 customers a day=R46x 7 days =R322x4weeks(month)=R1288x12months=R15456, this is how much your cashiers could be making out of plastic bags that they charge us and they take the money at the end of shift, this figure can be higher since u serve more than 100 customers a day...this is THEFT and not acceptable..i pay attention to my slips, many people dont!!!