scenario for give customer money
1- if customer c1 has transaction t1 with amount 1000.
2- we have a receipt for t1 with amount 1000.
3- if customer c1 return some goods for transaction t1 with amount 200.
4- we create return sales order and credit memo transaction with amount 200.
5- customer c1 didn't deal with us again .
6- so need to give the customer 200.
how we make this scenario ?