Mercari Got scam using this application Internet

I have nothing but bad experience with this service. The last one I totally lose money and left with a piece of crap. Contacted Mercari CS like a hundred times after I receive the item and got no reply. Then automatically they decided that the transaction was complete and then close it which released the money to the seller. They still won't reply to any of my messages. According to their rule if I disputed and item I should report it before the 3 days and I reported it right away as soon as I got it and see that the item was not working like the seller advertised. Well, till now no reply from Mercari. I want my money back and they could take this piece of junk. Im so tired of trying to get a hold of their customer service because they seemed all dead and nobody replies! This application need to get shut down!