How to create the Service confirmaiton customer return

Dear Experts,

In our business case,we use customer contracts process.

Create customer contract --> Trigger Service confirmation to issue the materials (Sales Item Group Code "DIGI")

My question is:Last month we had issued some materials via service confirmations and now customer has returned the materials due to wrongly ordered.

We can not cancel the service confirmation since the accounting period of last month was already closed.

I have tried the New customer return notification & New parts return notification. In neither case the customer return is not possible.

Can someone please help me how to take back the goods into stock and credit the amount to contract.

Regards,

Sriram