India’s Sistema Shyam TeleServices (SSTL), which offers services under the MTS brand, today introduced a range of “data plans for internet calling,” enabling subscribers to make national and international long-distance calls using any voice service app such as Skype, WhatsApp and Viber.

The VoIP apps could lead to cost savings for consumers of up to 50-75 per cent, compared to using regular mobile networks, and the move is designed to boost the company’s voice-centric data services business.

The CDMA operator, one of the country’s smallest carriers with less than one per cent market share, offers nine different plans for prepaid and postpaid subscribers. It said the INR499 ($7.63) a month plan, for example, gives users 5GB of data, which they can use to make 5,000 minutes of internet calls.

It is promoting the data plans as a “net-neutral internet calling option”, following a backlash in India back in April over the introduction of zero-rating plans. Two of the most prominent such schemes are Bharti Airtel’s Airtel Zero and Reliance Communications’, both of which have faced criticism from the country’s Department of Telecom.

This is not the first time SSTL has pushed “anti-zero-rating plans”. In August its new OpenWeb tariffs were launched “to provide absolute freedom to surf, call and chat freely and fairly”, according to its marketing.

The operator was the first Indian carrier to oppose the practice of zero-rating, describing it as counter to net neutrality and causing confusion among customers.

Its new prepaid internet calling packages start at INR198 for 1GB, while its postpaid plans start at INR599 for 10GB.