Selling laptops not meeting specifications

In November 2021 I purchased a laptop from takealot.com. On delivery the laptop (ASUS Zenbook) looked identical to the one ordered however discovered in December and reported early January 2022 that the specifications of the product supp**** did not meet those specified on their website. I contacted takealot.com and they advised that I need to return the laptop which I did. Options were provided and were asked to respond within 24 hours which we duly did (within less than an hour). A few hours later we received a notice that we did not respond within the deadline and our account summarily credited (again your mistake, we responded well within the unreasonable deadline). The same laptop that we originally purchased are available on the takealot.com website however at an increased cost. Why should your customer suffer and pay for the increase in cost as a result of your mistake/negligence? Since this was not acceptable we requested that the laptop be returned to us which you agreed to in writing. After not receiving further correspondence I followed up and your representative advised that it is no longer possible despite you agreeing to it. First you provide the wrong product (looks exactly the same as the one on your website however not the same specifications/internal components) and then you can't return it after you committed to do so? I asked to be put in a position where I am not worse off as a result of your mistake/negligence which you declined. How can this be right or fair to your customer?