i am a contractor, i have completed a road work project in npcil. in my contract my rates were inclusive of all taxes. I wrongly raised invoices for service tax but total value not exceeding my bill,as my rates where inclusive of taxes.services tax is exempted for road works,hence later i corrected and submitted my bills stating i had wrongly given invoices.now npcil is held my amount valuing to my service tax. help me to claim my money back and how i can sue them