Hi
When you made a payment to Vendor against a demand draft, the accounting entry would have been
Vendor A/c Dr
To Bank
You would probably have cleared a Venfor invoice or a it would be a downpayment. You need to use FBRA if invoices have been cleared. In FBRA screen give the document no and company code with fiscal year and than click on reverse. You will get a pop up for reset or reset and reversal. Just use the option Reset and Reversal. You should be able to reverse and reset the cleared items. In the Document No you have to specify the payment document no
regards
Sanil Bhandari