Unsatisfactory Device: Untruthful Marketing

I visited Vodashop Cape Gate-52479 intending to upgrade my Sim only contract and add a Smar****ch to it. My preference was not in stock where upon the Consultant marketed an alternative which he claimed to be much better to my preferred choice and also cheaper. I signed up to this device, however when I started to use the device, I found out that the promised functionality as marketed and demonstrated to me of the smar****ch were not on the device sold to me. I only discovered they demonstrated the promised functionality on a different model to the one sold to me. I then decided to act on my right as prescribed by the Consumer Protection Act and return the device, but they are adamant that I should keep it. The Consumer Protection Act stipulates that for directly marketed goods there is a cooling off period, but they insist I keep the device, which they falsely claimed and demonstrated as offering the functionality I was looking for. For this false marketing I don't want this directly marketed device anymore. I would rather have my own preferred choice, or non at all.