Welcome to the forum.
I'm not sure if you're picking a good name for your service, because the first time when I see your domain name, I automatically think your service is a tumbler/mixer.
If you have Tor version it will be better since you're promoting "anonymity".
We do not charge a fee for refunds. The return of tokens is done by sending the private key where your funds are stored, or, in the case of coins, a form will appear on the exchange page where you need to enter the address to which you want to return the funds and click the "Submit" button. After this, your funds will be automatically returned to you.
Even though it's a good thing you want to refund the money and covered the transaction fees, but I still don't like the way you make Bitcoin as non fungible.