Hi,
in this case it would be easy if you set an outgoing payment method on the contract account, no manual actions would be required and the credit would be picked up by the payment run and refunded to the bank account mentioned in the outgoing bank details Id on the contract account. Another solution could be to create a payment specification using transaction 'FPAY1A' (Create for Payment Run), in this case you can set a payment method and a bank detail ID on the payment specification, even start a workflow to approve it using event 5514, and no changes need to be done on the contract account or on the open credit items.
Best regards,
Adriano.