Product: Credit card or prepaid card

I made a purchase on XX/XX/XXXX from XXXX XXXX XXXX XXXX for amount XXXX USD amount. The guy came to my XXXX  a couple of times and introduced the big promotions that their company was having before the XXXX XXXX. I have been planning to buy those items ( Fridge, stove, and dishwasher ) for a while and thought Id do me a gift for XXXX. I trusted the guy and made that purchase when he came over again. He showed the items on his tablet, we took measurements and he processed the payment on his tablet. After the payment, I got a text receipt on my phone and nothing was suspicious to me, at that time. He told me that it would take a couple of days before theyd make delivery as the merchandise was custom made and they had to get it ready. I never received it during the time they were supposed to deliver but the guy was promising that Id get it. After the XXXX XXXX, the guy came again, and I told him that I am canceling the order. He promised that Id receive a refund during a couple of days. I also asked to provide me written proof that I cancelled the order ( See attached ). 
I was already full of frustration and doubts that something wrong happened and I called my bank ( Chase ) to dispute the transaction. I also went with my boyfriend to their physical location but couldnt find them. I really started to get worried. 
I submitted the details on my Chase account, and someone told me that it will take time to investigate. On XX/XX/XXXX I got a phone call from someone from the Bank who left a voice mail asking to call him back and there was also another phone number in case he didnt respond. I called him and he didnt respond. I called to the other number and talked to a guy who said that everything is fine, and the case is still under investigation and nothing needs to be done. On XX/XX/XXXX I received an update that THE BANK considers the disputed charges valid. I was really surprised and frustrated and called the number provided. I talked to Chase specialist and explained the situation, we talked almost 1,5 hour and went through everything. During that conversation, I found out there is a document that hasnt been uploaded. She advised me to put a request to reopen the case. I uploaded the document and requested another investigation. On XX/XX/XXXX received a note saying that the result of additional review confirms that the transaction is valid, and no billing error occurred. The news was shocking for me and I called in again. The Chase representative I talked to was also surprised by the decision and suggested to schedule a call with a manager. 
The manager called me the next day and told me that the reason that decision was made was that they sent me a message on my account on XX/XX/XXXX which I was supposed to sign and resubmit which I never did, as I never received any notification about it. He came up with a new story and according to him they never even made the second investigation as that paper wasnt signed. Meanwhile, the official letter I received on my Chase account stated, the result of our additional review confirms that the transaction is valid. I never received any notification that there was an update on my case. After he told me I found the note on my Chase account, but I never got a notification about that. That was a big amount, and The Bank stopped the investigation because of some paper that I never received. Usually, those kinds of important paperwork are supposed to be sent by mail. Besides, I called back after someone left me a voice mail and talked to a representative who said that there is nothing needs to be done at that moment. 
This case is about a big amount and we cant count on just sending an e-mail which can easily get lost in Spam. I was trying to explain to him the situation, but he was indifferent and seemed he didnt care what happened in reality. He just told me that there was nothing that my bank could do, and I had to find the merchant which was a scam and I was trying to find them for a while already. He told me that it was my responsibility. Also, no one ever told me about this before. 
The fraud company took the money and disappeared, and the bank doesnt want to do anything while having all the proving documents. I am really lost and dont know what to do. It seems that they are using this Covid situation to just close the case without really investigate the matter. 
Please help me Thank you