While checking your TOS, I found something I haven't seen at any legit online shop. Is that really how you treat your customers, not allowing them refund at all?
https://shop.bitmain.com/product/detail?pid=00020221030110209340BlAGIXVS065E4. After an order has been submitted, a request to cancel the order, refund any part of the ordered amount or change the ordered item(s) to different item(s) or different batch(es) will not be entertained by BITMAIN.
They all do post this but it's mostly just on the surface, just as people do manage to cancel orders and get refunds from Bitmain, as you can see they agreed to send back the funds to the original wallet, so they agree on a refund but with their conditions.
It's just stupid at this point of course they could make an exception especially since OP is having a meltdown and is probably one inch away from a heart attack but at the same time, you just can't just send funds to a different wallet that easily, especially since the buyer changed his mind a few hours after the order. What if he used somebody else account and coins to pay?