You basically have to catch it before the charge is even settled; either within the same business day before your settlement cutoff, or by authorizing without capturing for a day or two so you have time to review. Once the charge is settled, a refund almost never stops someone from charging back the payment -- for whatever reason, when a card is reported stolen, people and banks simply charge back everything unauthorized even if a quick review of the account would show some of the payments were already refunded. You can dispute these chargebacks by providing proof of the previous refund, but you're still out the chargeback fees, and these chargebacks still count against your account -- so they can end up getting you terminated if your CB rate is pushed too high.
We get these, have seen a case where we refunded but apparently they were going after the currency conversion amount with the chargeback. Do some providers offer longer settlements? Feels like we only get a few hours a lot of the time to void a transaction.
You have 1-3 days to capture an amount you previously authorized. You only have so little time because you're authorizing and capturing at the same time. If you need more time to review, decouple them. Some payment gateways also let you decide the settlement cutoff time, so you can set it after business hours.
