The Supreme Court has sought responses from Bharti Airtel and Vodafone Idea over the Centre's challenge to the Bombay High Court ruling against retrospective one-time spectrum charges (OTSC). The levy, first demanded in 2013, totals around ₹22,000 crore, including ₹3,300 crore in bank guarantees. The Centre argued spectrum is a public resource and operators must pay its market value.