Bad service

I bought a petrol pump relayed on the 2nd of December 2020. When I got home, I realized that they gave me a wrong item. But because I was busy at work, I didn't have time to return it on the day. I only had time today which is the 9 of December 2020 to return the item. When I got there I was told with a bad attitude to read the T&C on the receipt. Their receipt says no returns allowed on electronic items, which I understand. But my issue is, why did the sales person sell me a wrong item? If he sold me a correct item, I won't be returning the item. I can't just throw away R200. I asked for their head office number or owners number. They refused. I need to talk to their senior.