Customer service needs improvement

I am referring this complaint or suggestion rather to the Ok foods that is located in Potchefstroom, North West shoping complex. The lady in management I'm not certain if whether is an assistant manager or something. She gave me the looks of decifullness this other time during the week as I was buying some essentials because I had gotten in with two previous plastics from checkers. Instead of her mentioning this to me beforehand whilst I was paying for my essentials, she let me be with her bodily facial expression showing otherwise. As I was outside I remembered that I had forgotten to buy spices inside so I quickly go back inside the shop to see if those spices are still available and as I entered the shop she storms behind me telling me in English that I'm not allowed with my plastics inside the shop because the items are still sold in store. My question is why didn't she mention this to me earlier and is it a crime for a customer to forget doing so? I will kindly await the response from the institution, Thank you.