Takealot not delivering correctly

We bought a Canon Pixma G6040 inktank wifi printer for R7000 a couple of weeks ago. Today a Canon printer cartridge 445 was delivered worth probably R300 to R400. Totally wrong item. Upon enquiry, we were told the item is out of stock and we can get credits for the amount paid. When we purchased the printer it was not out of stock and you gladly took our money. We run a small business and have been patiently waiting for the printer which is out of stock. Moreover a totally wrong item was sent. What went wrong? We have been faithful clients of Takealot over the years and have spent hundreds of thousands of Rands. Now this. How is this kind of mistake even possible?