Product: Credit card

I made a purchase XX/XX/XXXX, returned item scanned by carrier with tracking XX/XX/XXXX. This is verified on vendor website and is shown received XX/XX/XXXX. Vendor notes receipt to warehouse on XX/XX/XXXX and I confirmed with vendor via recorded call. The bank claims that the vendor is saying they did not receive goods, although I provided 12 screenshots from vendor website which track progress of item being received, scanned, classified as returned and " refunded '', emails from the vendor acknowledging receipt of goods, and vendor noting on the website that a " refund '' has been made. Vendor says I must get refund from bank. I have spent hours on the phone. I sent 12 screenshots to the bank via the link with case number that the bank sent me, documentation via regular mail back to bank that they sent me, and the bank is now saying that the case number that they sent me won't work and I have to repeat the process after hours and hours of recorded calls with them. I have spent hours on the phone with vendor and have dozens of emails, despite tracking and website screenshots showing the return. Please see chronology of events below. 

*First Capital One made an error on XX/XX/XXXX ( reference letter ) charging me back {$490.00}, for the entire order amount. I did not return the entire order. Instead, the matter in dispute was {$350.00}. Why Capital One charged me back {$490.00} remains a mystery. 

XXXX made a purchase with a vendor and returned an item valued at {$350.00} on XX/XX/XXXX. It was scanned in by the carrier and acknowledged on the vendor website. 
*The vendor has a " Refund at first scan '' policy which I was expecting to avail myself of. 
XXXX watched for the refund and after several weeks still didn't ' have it. I tracked the progress, noting that the vendor had scanned the item in, and received emails from XXXX customer service confirming. 
*After nearly 4 weeks without a refund, I called Capital One to ask for assistance. The agent credited me back the subtotal, on XX/XX/XXXX ( {$320.00} ), and I called back on XX/XX/XXXX to ask for the remaining amount of purchase ( {$31.00} ) for the total return amount of {$350.00} *The vendor acknowledges return and credited me, but just for the tax (??? ) *Capital One charged me back for the subtotal and the tax ****I called Capital One and the agent told me that XXXX said they had NOT received the item ****I called XXXX and they said I had to speak to my credit card to wait for credit ****I have more than a dozen screenshots and additional emails proving that I sent the item back, tracking number proving that the vendor received the item, emails that substantiate that the vendor received the item ; all of which I provided to Capital One when I was sent a link from your customer service on XX/XX/XXXX. 
*When I called back today after nothing that I wasn't credited after sending significant proof of return, I was forced to spend nearly an hour and a half repeating my situation and told by XXXX XXXX XXXX and XXXX that my case ending XXXX was void. The paperwork I sent via mail, and via email link could not be used! I would have to resubmit all documentation under case XXXX, a case number I had never heard of, nor gotten requests to address. 

This is egregious. I have significant proof which I can provide.