Amazon Makes Mistake Then Why I Must Pay Shipping Fee for 48-220 Volt Changeover  Inverter Mishap

I bought a 48-220 volt changeover inverter from Amazon. The seller deliberately sent a different product. Because he knew very well that if I returned it, I would have to pay the shipping fee and that I would give up returning it because it would be costly. I wanted 48 volts, the seller sent 12-24 volts. When I wanted to return it, the seller sent me a message and said, 'Don't return it, I'll give your money back.' The seller made a mistake, why am I paying the shipping fee? Moreover, I have been waiting for this product for 15 days. Amazon cost me time and money. Amazon is not around at all. The text keeps popping up saying our business partner's robot will answer. Amazon If you don't solve my problem, this will be my last purchase from you.