India's Reliance Communications lost more than 13 percent of its mobile customers in July as it cut off inactive subscribers who have not used their phones for two months, although the firm said the move would have no impact on revenue.
About 95 percent of the mobile phone users in India, the world's second-biggest mobile phone market, are prepaid customers and many have multiple accounts.
For the last year or so, carriers have been cancelling inactive accounts in a clean-up exercise, as focus shifts to increasing revenue rather than flaunting customer base.
Tata Teleservices has reported a decline in customer base several times in the past months after the clean-up began, but the 20.5 million customer cutoff is the first time Reliance Communications reported a fall.