PIC N PAY FALSE ADVERTISING

I went on the pic n pay ASAP app and they advertised Milo Breakfast energy drink 200g at R6. 99 each. I proceeded to order 20 boxes for me and my mom and sister in law. R139 plus R35 shipping. All went as should and i paid. Then just befor deliver i got a notification that my order was changes (without asking me if i want proceed with what was left of the order). Then when i got the order i was horrified that they sent me 9 x single small sachets and not the 20 x 200g like they advertised.... I have schreenshots of the add and all my orders and their amendments. This is FALSE advertising! If i had known this is how sly they are going to be i would have canceled my whole order. I def want what was advertised or all my money back in full! I will be going to social media if this is not resolved.