KOLKATA: Anil Ambani-headed Reliance Communications has unveiled, what it calls, a disruptive data plan which promises data usage at a monthly rental of Rs 999 with no download quantity caps whatsoever, a move which comes barely 24 hours after Bharti Airtel said it would offer 4G services at or below 3G rates.The back-to-back moves could mark the beginning of a bruising data tariff war as telcos move to garner as many higherpaying data subscribers as they can in the run-up to Mukesh Ambani-owned Reliance Jio Infocomm’s expected 4G services launch next year. The Sunil Mittal-founded Bharti Airtel, India’s No. 1 carrier, had said on Wednesday it would offer 10 GBs of data on 4G at Rs 999, which is 33% cheaper than its 10 GB data variant on 3G, priced at Rs 1,499.RCom’s unlimited data offer, launched on Thursday, directly takes on rival CDMA operator Sistema Shyam Teleservices’ identical Rs 999 data plan, which has 40GB and 20GB limits for postpaid and prepaid customers, respectively.Gurdeep Singh, chief executive (consumer business) at RCom, told ET that the move is aimed at grabbing potential data customers from rival networks who are “dissatisfied with their current data speeds or the quality of indoor coverage”.The company’s unlimited data plan at unbridled data speeds up to 14.7 Mbps would initially go live in Chennai, Bengaluru, Hyderabad and Pune and eventually be extended to other key cities including Delhi and Mumbai.Singh stressed that the plan “was truly unlimited”, in that, a customer opting for it could safely go ahead and download, say, “100 GBs for Rs 999 without fear of a bill shock at the end of the month”.The offer “was not a promotional offer in disguise to grab data customers in key markets. We are here for the long haul and plan to extend this offer nationally in all key markets,” he added. RCom will be in direct competition in Bengaluru and Pune where Bharti Airtel operates 4G services, while it would be sparring with the Indian unit of Russia’s Sistema JSFC in Chennai and Bengaluru.Till the time of filing report, Vodafone India, Idea Cellular and Sistema Shyam declined to reply to ET’s queries on whether they would also slash 3G data rates or go unlimited.Lately, India’s top mobile operators have been cherry-picking lucrative data customers amid surging demand for data services and also in anticipation of fierce competition on the 4G front from Jio which is widely expected to launch its own 4G services by March next year. Higher margin data services are expected to drive revenue growth at India’s mobile phone operators in the coming years.At the end of September, non-voice revenue, including from data, made up over 24% of RCom’s telecom revenue, and over 20% of Bharti Airtel’s mobile services revenue. Both Bharti Airtel and RCom had over 15 million 3G customers as on September 30.Industry experts, however, are sceptical about RCom’s offer, arguing that it is “technically impossible” to offer unlimited data downloads at the promised speeds over a long term to a large customer base as it would choke up the network and disrupt mobile coverage.“Since a data pipe’s capacity is finite, a large group of customers collectively opting for such an unlimited offer are bound to experience a serious loss of speed at some point, especially since DoT allows operators to downgrade data download speeds as part of its fair usage and trade policy once a customer is seen to be abusing a data plan,” a top executive of one of India’s biggest telcos told ET on condition of anonymity.