Online site ***********

I ordered items on promotion on the Bash app. The promo was for buy two products and get the second one 50% off. No one told me anything about an item out of stock. I recieved one parcel today. When I enquired about it, they keep on telling me the same thing that they have cancelled the one item on order, so I must now go but the item seperate and pay the full price on the item? That is not fair, please sort your issues out as soon as possible as I need the items,