If a shopper for some reason wants the funds returned from a merchant, they can ask the merchant to make a refund. If the merchant refuses, a shopper may ask their issuer to make a chargeback (sending the funds back from the merchant to a shopper).
After a chargeback is initiated, the merchant can dispute it in some cases. If a dispute is allowed, the merchant should provide all necessary documents to either the acquiring bank, or to the payment processor.
When possible, Adyen helps its merchants to automatically dispute chargebacks, and also provides extensive risk management services (RevenueProtect) to analyze fraudulent transactions and minimize chargebacks.