Boxer puts items on sale only just as a ******* 😡

I bought a home mini ovenon the 23 April. I went to Boxer Senaoane today to ask for a refund as it is not hot enough to cook my food to the maximum and I have already bought a bigger stove and I don't need this one anymore. I still have the original till slip. I was told I am not able to get a refund and that I can only exchange for other items. I do not need this stove anymore, should I now be forced to keep this oven knowing that I will never use it?