How do I record a refund of a Prepaid Voucher?

A purchase order was created for services to install a machine.  The PO is for $6,800, we had to prepay 50% down.  We created a prepaid voucher in A/P, we have paid the $3,400, 50%.  Now the PO is cancelled and the company has returned to us the $3,400.  I need to know how to record the refund of $3,400.  I still have the $3,400 credit prepaid voucher still on hold.

We are on JD Edwards World A9.3.1.3.

THANKS

Peggy