India’s largest mobile operator Bharti Airtel filed a complaint against bitter rival Reliance Jio with the country’s competition regulator, accusing the upstart of predatory pricing and of abusing its dominant position.

In a letter to the Competition Commission of India (CCI) Airtel claimed Jio, as a unit of India’s largest enterprise Reliance Industries, is a dominant player in the telecoms sector after investing about $25 billion, the Economic Times reported.

Jio said it signed up 72 million customers since its official launch in early September.

The market leader argues Jio’s free service is predatory in nature according the Competition Act.

In its letter, Airtel said: “It is a strategic business tactic adopted to enhance market power with the objective of eliminating competition, which it has succeeded to a large extent during the quarter October to December,” according to ET.

Airtel, Vodafone India and Cellular Idea have been hit by the generous free voice and data offers introduced by newcomer Jio. The country’s three largest operators have all been forced to introduce expanded data offers.

In January, Airtel reported a sharp drop in profit for its fiscal Q3 as lower data and voice tariffs in its domestic market pulled down its turnover for the first time since 2002.

The Telecom Regulatory Authority of India (TRAI) last week rejected petitions filed by Airtel and Idea questioning the validity of Jio’s extension of its free offer until end-March. After TRAI said Jio’s special new year offer does not violate regulatory guidelines on promotional offers, the Telecom Disputes and Settlement Appellate Tribunal is expected take up the matter this week.