Reliance Communications Ltd , India’s fourth-biggest mobile phone carrier, will hike voice prices starting April 25, the company said in a statement, to counter an increase in input costs and higher spectrum payments.

Reliance will increase tariffs on discounted and promotional plans for its pre-paid customers by up to 20 percent and raise headline call tariffs to 1.6 paise every second from 1.5 paise, it said in a statement on Tuesday.

Reliance and its main rivals, including  Bharti Airtel Ltd , India’s top phone carrier, and the local unit of Vodafone Group Plc , last year raised voice prices for the first time in three years as they continued to cut discounts previously offered to lure customers in a highly-competitive market.

Carriers have seen the benefits of reduced competition after several smaller rivals were forced by a court order to either shut down or scale back operations.

“We continue to focus on growing profitable/paid minutes on our network and the current tariff hikes are part of our continued efforts to reduce free and discounted minutes, and offset the ever-rising costs of input materials,” the company’s chief executive officer, Gurdeep Singh, said in the statement.

Indian carriers receive more than 80 percent of their revenue from voice call services.