Aditya Birla Telecom (ABTL), a wholly-owned susidiary of Idea Cellular, on Thursday said it would dilute 20 per cent stake to US-based private equity firm Providence Equity Partners for Rs 2,560 crore. "The fund will be used to carry out the firm's network roll out and ongoing expansion programmes and for future use," Idea Cellular's Managing director Sanjeev Aga said in Mumbai.