Product: Credit card or prepaid card

On XX/XX/2019, I opened two credit disputes with a merchant -- XXXX -- for two payments made for the same product. One was for {$430.00} and the other was for {$1200.00}. 
The following week, I called Citi to make sure I was providing all the information possible to support my claim and asked if I could do more, such as provide photos or other evidence that the cups weren't able to be separated. Citi said that I've done all I can do and that I needed to wait 45 days for a response from the Merchant. 
On XX/XX/2019, I got a notification from Citi that the merchant had responded to my disputes. Citi asked me to provide a signed letter and address the merchant 's response, along with proof of return and documentation that supports my position. At this time, I only saw one letter come up on my Citi portal, so I addressed the {$430.00} dispute. 
On XX/XX/2019, I submitted my response for the {$430.00}, detailing my position ( as asked ) for why the cups were defective. I also explained that the merchant would not provide return shipping, though I asked them to twice. I also explained that the merchant provided INCORRECT information about the wrong case. They presented their case with bad information, which I pointed out in my letter. 
On XX/XX/2019, I saw and submitted my response for the {$1200.00} dispute. The response was identical to the response for the {$430.00} dispute. I detailed my position ( as asked ) for why the cups were defective. I also explained that the merchant would not provide return shipping, though I asked them to twice. I also explained that the merchant provided INCORRECT information about the wrong case. 
On XX/XX/2019, Citi notified me that my dispute credit of {$430.00} had been made permanent. 
On XX/XX/2019, Citi notified me that my credit of {$1200.00} would be reversed and billed to me. I called Citi to ask why and spoke with a supervisor named XXXX. I couldn't get a straight answer from XXXX. At first, she said Citi attempted to go to pre-arbitration. Then she said they went to arbitration but Visa declined because they didn't have enough proof. I pointed out that the merchant didn't provide ANY proof because they sent a response to the WRONG case and XXXX told me that " we all know what they meant ... we're talking about the same thing. '' XXXX then told me that Visa requires proof of return. She then explained that there might not ever be proof of a return if the merchant doesn't accept the return. I told her that the merchant would accept the return but that they didn't provide the label. I had made the merchandise available for them to pick up and they didn't come. I explained that I did everything I possibly could to return the merchandise to a merchant who would never accept it and XXXX explained that Citi can't help because Visa won't accept the arbitration. XXXX talked over me so I'm not sure she ever actually heard me. She was very difficult to work with and it took me so long to try to understand what she was saying because she gave contradicting information. I asked why one charge dispute was made permanent and one was reversed when the cases were identical and she said that one must have been just for the downpayment, which didn't require merchandise to be sent back. I reiterated that the letters from Citi, the response from the merchant to the WRONG cases, and my responses were identical. I doesn't make sense that one charge was reversed while the other was made permanent. XXXX just reiterated that it was because Visa wouldn't accept the arbitration and that there was nothing Citi could do.