Received job work material accounting

Dear Sirs,

  i m working in a manufacturing company.  My query is

 We receive the raw material from our customer  with due invoice for Rs.175 for example. And we add our raw material with material received from customer ( say mixing 75% of  both the materials). After completion of process we sold the Finished goods to customer with due invoice for Rs.100/- according to usage of both material (ours and customers).we will be receiving the payment for Rs.100/- But in ledger its stll showing credit balance in customer (debtor) ledger.

    Kindly advise in this regard. and Please guide me further for accounting and settling the account same in  books.

Thanks and Regards,

 Murthy