post https://api.sandbox.rainforestpay.com/v1/payins//void_or_refund
Void or refund a payin by the payin ID. If the payin processing has not completed, then the payin can be fully voided. If the payin processing has completed, then the payin can be fully or partially refunded. A payin cannot be partially voided. The merchant status must be ACTIVE to void or refund a payin.