Is Game Online Store trying to rip me off

I purchased a Defy Gas/Electrical oven from Game Online on the 8th July 2020. I accidentally purchased 2 x units and immediately informed them that I made an error in purchasing. I raised an online ticket and did not receive any news and kept on raising tickets until a Cedric, employed by Game, contacted me to confirm acknowledge of my query. He stated that he was going to confirm delivery and my credit but only contacted me once. I have raised or added to my tickets since that conversation with him. The eventually delivered my oven, after numerous calls to their warehouse and my dad accepted and signed for delivery of the oven. He made a note on the physical delivery note stating that he is returning the one unit, added his ID No. for good measure and signed it. Game has now sent me an email confirming delivery and acceptance of both units. I have requested a copy of this delivery note. I am frustrated as my order history shows that I have accepted both units. I feel that someone is trying to rip me off with R9 499.99 and I have demanded answers on so many occasions to my query.