Misleading advertising

The fish and chips normally come with 2 pieces of fish. On the entertainer app they had a special buy 1 get 1 free. However when I ordered it, it only came with 1 piece fish each. This is a *******. Why say buy 1 get 1 free when you taking 1 portion and putting it in 2 plates. This is very misleading and this information should of been shared beforehand