Terrible on line shopping experience

I am disgusted and annoyed with my very first and definitely my last on line shopping experience. The substitution of products makes no sense! How can you give me products that cost more than I agreed to pay! No where on your online page does your substitution policy say that you will decide the price I will pay for the goods that you are out of stock with. Also, if I buy 2 litres of oil and you do NOT have it in stock, why would you give me 2 X 750ml bottles at more than the price I agreed to for 2l??? Does that make sense to you? And Samantha who is apparently in charge of the on line shopping had a bad attitude and was unhelpful! I am so angry with PNP I will move my business to Checkers!!