Airtel arranged in October to acquire Tata Teleservices' consumer mobile business, including its 40 million customers across of 19 of India's 22 telecoms circles.
Airtel is now transitioning Tata Teleservices customers into its operations under an intra-circle roaming agreement, the Economic Timesreported.
But Indian regulator Trai may raise objections to the move on the grounds that Airtel is violating the agreed procedure by automatically transferring customers.
An official at Trai told the publication that customers have the right to select an operator of their choice, and automatically migrating them to Airtel may violate this right.
Airtel has asserted that the ICR arrangement does not curtail customer choice and that the customers will continue to be Tata Teleservices customers while accessing the Airtel network.
But the company did not explain why Tata Teleservices customers with existing SIMs are being automatically shifted to Airtel.
The new customers were only part of the draw for Airtel's acquisition – the company is also expected to secure 178.5 MHz of spectrum across the 850-MHz, 1800-MHz and 2100-MHz bands as well as a right to use part of Tata Group's fiber network.