Bharti Airtel, India’s largest mobile operator, raised the stakes in the country’s data pricing battle by offering customers who upgrade to a new 4G handset 3GB of free data a month for 12 months.

Market leader Airtel, responding to 4G newcomer Reliance Jio’s generous free offers, last month introduced prepaid data plans with free voice. In early December Jio extended its free voice, data and video offer from the end of 2016 to the end of March, as part of its new year offer.

Second-ranked Vodafone India and number three Idea Cellular also launched free voice plans or expanded prepaid 4G data allotments last month.

The operators’ defensive moves are aimed at retaining their prepaid customers as Jio’s free offers attract low-end users.

Airtel’s latest offer, available to new or existing customers until 28 February, gives prepaid and postpaid users an additional 3GB of data a month until the end of the year.

Its standard prepaid plans offer free voice calls and 1GB of data. Prepaid users will receive an additional 3GB of free data with every INR345 (about $5) recharge. Customers on postpaid plans with data allotments of 3GB to 8GB also will receive 3GB of free data a month. The postpaid plans also include free unlimited calls and SMS.

Airtel said postpaid customers can obtain the free data through the MyAirtel app.