Isn't there room for abusing this ?
Someone could buy something in your store for 100$ worth of bitcoin. Now Bitcoin prices drop and he asks for a refund for 100$. Now he can just buy back more bitcoin essentially. If the price of bitcoin rises however, he could ask for the bitcoins back and buy the items with fiat currency and sell the profit in bitcoin he made.
I'm pretty sure you need a proper reason to ask for a refund, and tbh, refunding for the sake of profiting doesn't seem to work as one ngl. And I'd assume OP's store would just return the fiat value back, whether Bitcoin increases or decreases since there should already be a plan for the stored BTC. Either putting a part of it as BTC to let it grow and converting the rest as profit, or just letting it all grow as BTC. I'd say it would depend on the number of transactions done on fiat and done on Bitcoin before OP decides on what to do. Someone could buy something in your store for 100$ worth of bitcoin. Now Bitcoin prices drop and he asks for a refund for 100$. Now he can just buy back more bitcoin essentially. If the price of bitcoin rises however, he could ask for the bitcoins back and buy the items with fiat currency and sell the profit in bitcoin he made.
Where I live (In Germany), you can basically return anything you bought within a few weeks in most stores.
If you damaged something or already used it up, that obviously doesn't apply but for tech stuff you just keep the receipt and return the product if you don't like it.
In this scenario, I could definitely buy something with bitcoin and profit from refund it
It's like shorting/selling bitcoin to fiat and if the price goes up, you just reverse it