REJECTED WARRANTY AFTER 1 MONTH USAGE

I bought an Essentials two plate stove at Eloff Street on this receipt : ********** 777 and the stock Worked for only a month. I sent the stove back Shoprite at Kagiso Mall But the lady by the name of RoseMary, Title: Admin Manager said that my stove was not acceptable due to the plates being dark and wanted the stove to be returned as "NEW". The stove after 4 or 5 times use the plates becomes dark due to Heat. I need a refund or exchange