Yes we have all data in our DB and also logs, but there is nothing to show - he really topped up his main balance with $100 and purchased one card, but he never actually used it. Later, he began posting fake reviews, claiming we are a scam and that we blocked his two cards without reason (when he only had one ACTIVE card with $10 on the balance and no transactions). He also claimed to have contacted support and spoke with AI, but we only started using AI in September, while his review was left in August—further proof he’s lying.
I'd say the best course of action here is to terminate access with this customer (which you seem to have already done) and send him back the main balance in the cryptocurrency he paid with.
Obviously the balance contained in a card is with the card issuer and can not be brought back, but unless your terms and conditions says that there are no refunds in case of account closures - I haven't checked the ToC thoroughly so I don't know for sure - then you really should refund whatever is remaining from the top-up balance. Probably $100-$10*5% or something, by now, I'm not sure.
As you can see, you're not being viewed positively by the other members if you withhold it.