Mycom Trading overcharge there products

I did business with them in January 2019 and told them that their prices were double the prices that I paid for the same product at Waltons and that I do not want to do business with them anymore. Now suddenly they come up with a story that I still have an order standing. They first sent me the invoice for a product that I did not ask for and then sent me the correct product but with a price more the 270% higher than what I pay for at Waltons. Their price is R1199 and Waltons price is R444.05