The refunds are designed to protect merchants from receiving a chargeback and chargeback fee. However, occasionally you might receive a chargeback after the issued refund.

The main reason for this issue is a delay in the issuing bank system. 

The second reason is that the user first reached the bank and filed a chargeback after contacting the merchant's customer service. In this case, the refund is issued after a chargeback was raised. 

The third reason for the issue might be that the client requested a full refund, but a partial refund was performed. The client also may contact the financial authority to request a full refund. 

The fourth reason is the refund failed due to technical issues on the issuing bank side. 

For any reason, if this situation happened, you can provide documentation for representment. However, please note that even if you win, a chargeback fee still will be applied, and the chargeback will be counted to the chargeback ratio.