False Advertising

I have just returned a delivery from Planet Ink (https://www.planetink.co.za/products/samsung-clt-504-colour-toner-cartridges-clt-k504s-clt-c504s-clt-y504s-clt-m504s-planet-ink-compatible) and they are refusing to refund. I returned based on the false advert that gives customers the impression that the advert is for a set of cartridges CLT-504S. The title of the add clearly states CARTRIDGES with an "S" for plural. It also lists the product codes of the the different cartridges in the add. When I received the delivery, surprise, only one cartridge was received. I returned it and guess what... They don't want to refund cause I opened the package. How I am supposed to check what i received without opening the box, is beyond me! I am at a loss for R999 from these ********. Don't use them!