I don't know if it is possible where you live, but can you demand a refund without returning the device?
That's how people in China countered fake 2TB thumb drives on taobao. They knowingly buy the device and ask for refund (because it's fake) without returning. They have an online forum full of "which merchant is selling fake drives today".
The trick is there are "Mass Production Tools" (I think it actually means firmware configurator) for the flash controller used in these scam drives, which can turn them back to their original capacity (usually 4GB or less). So by doing so they effectively win some free tiny-ish thumb drives.
In England & Wales, goods must correspond to their description [Sales of Goods Act]. If not then the seller must offer a full refund including the cost of returning the mis-sold item [Consumer Rights Act and other acts relating to the implementation of the EU Distance Selling directives].
If all or part of the payment for an item is made with a credit card then the credit card issuer is jointly and severally responsible ["Section 75"]. So if a retailer doesn't play along will find themselves answerable to their payment processor; the customer doesn't have to get involved.
It's not unheard of for sellers to issue a refund and request the customer dispose of a faulty or mis-sold item instead of bothering to return it. But that's only if the customer is OK with it; if I wanted to return, say, a washing machine and the seller refused to co-operate then I'd be in my rights to dispose of it at my expense and refund the balance minus my reasonable costs to the seller.
That's how people in China countered fake 2TB thumb drives on taobao. They knowingly buy the device and ask for refund (because it's fake) without returning. They have an online forum full of "which merchant is selling fake drives today".
The trick is there are "Mass Production Tools" (I think it actually means firmware configurator) for the flash controller used in these scam drives, which can turn them back to their original capacity (usually 4GB or less). So by doing so they effectively win some free tiny-ish thumb drives.