Vendor return in for imports

All SAP Gurus,

We have created the import's PO.

In the PO we have given Basic price, Customs duty and CVD values correctly, but forget to enter freight cost.

GR has been made (excise invoice captured), material also cleared from Quality (UD is done).

Now, we want to add freight cost:

1. so that the freight cost will be inventorised

2. Payment can be made to vendor

How this can be done now?

(All options including cancellation/reverse of material document, vendor return are open for us.)

Regards,