Service tax on royalty

DEAR EXPERTS,

WE HAVE PAID SERVICE TAX ON ROYALTY THROUGH CENVAT CREDIT BUT ACCORDING TO REVERSE CHARGE MACHENISM WE CAN PAY SERVICE TAX ON ROYALTY THROUGH CASH ONLY. NOW SERVICE TAX DEPARTMENT RAISE  A DEMAND THAT TO DEPOSIT ALL SERVICE TAX IN CASH ALONGWITH INTEREST ONLY. CAN ANY ONE SUGEST ME TO COME OUT THIS PROBLEM WITHOUT ANY INTEREST. ULTIMATELY WE HAD PAID SERVICE TAX  THROUGH CENVAT CREDIT.

THANKS