GSM-based service providers have demanded a refund of Rs 2.25 billion from DoT. The refund demand is in lieu of extra charges paid by them in financial year 2004-05. The amount could be close to Rs 3 billion for the current financial year. According to the COAI, GSM players have to pay 4 per cent of their revenue as spectrum usage charges, as against 2 per cent for CDMA operators.