Complaint sub-issue: Credit card company isn't resolving a dispute about a purchase on your statement

OnXX/XX/XXXX my friend and I attended the XXXX Home and Garden show where we each made a purchase from a merchant XXXX XXXX XXXX, XXXX XXXX, CALIFORNIA. My purchase was for {$4200.00} and his was for about {$800.00}. Later that day we decided to return the products and called the phone number on the sales receipt and we were told to come back to see them. We immediately returned to the booth where the products were purchased with all of the products in their original boxes unopened and requested our refund. At no time during the sale was I told this was a final sale, no returns. During the demonstration I point blank asked the salesman if the merchandise was returnable and he assured me it was. When I arrived I was greeted by salesman that sold the merchandise earlier that day. He tried to talk me into taking additional merchandise and also wanted to upgrade some of the products. When I refused the additional products and merchandise he refused the refund. I asked to speak to his manager he called him and in a few minutes he came over to the booth and told me that I had signed the receipt that said no return no refunds. At no time during the sale was No returns, Final sale mentioned and It also was not posted in their booth. During the demonstration of the products I asked about their return policy and was assured that I could make a return. Because the manager of XXXX XXXX XXXX refused the return, I then went to the management office of the Home and Garden show and asked to speak to the person in charge of their merchants. A few minutes later the exhibit consultant came out and said she would talk to the people at XXXX XXXX XXXX. While she was talking to them I contacted the US BANK number on the back of my credit card asking how I can avoid paying for the products I returned when they were refusing to give me my refund. I was assured that I could file a dispute and would not have to pay the charges. I made several calls that evening to the customer service number on the back of my credit card, each time I was assured that I would n't have to pay if I filed a dispute claim. When XXXX XXXX XXXX  offered to refund me 75 % of my money I again called the customer service number and they told me to take what I could get and to dispute the additional 25 % later. I then went back to XXXX XXXX XXXX with the exhibit consultant and they were going to make me sign an agreement not to dispute the remaining 25 % restocking fee with the credit card company. Why would I agree to pay a 25 % restocking fee when I saw the sales people restock the products that they sold to us earlier in the day? We called and started the dispute that same night when we got to my friends home. We both received letters from US BANK Flex Perks asking for information about the dispute in about one week we both filled them out and returned  them to US BANK. About two months later we were again asked to give additional information about the dispute. Later my friend got a letter telling him that the dispute was determined in his favor. I received a letter telling me that my dispute was denied. I called the credit card company and spoke with the person that signed my dispute letter she refused to make any changes I then asked for a supervisor who told me that my dispute was denied because I had signed the no refund no return sales receipt. When I asked why my friend go his charges refunded and I didnt he said he could not comment on another persons account.