Bharti shares surged 9.3 percent last week, the biggest weekly gain since late September.
Credit Suisse upgraded Bharti to 'outperform' from 'underperform', and raised its target price to 355 rupees from 225 rupees, citing greater clarity on the regulatory front and reduced competitiveness in the domestic sector.
The investment banks add operators could also be testing markets for tariff hikes by reducing discounts.
"While the recent rally in stocks has been led by easing regulatory concerns, we believe the next leg will be driven by tariff increases," Credit Suisse said in a note dated on Monday.
Goldman Sachs upgraded the stock as well, to 'buy' from 'neutral', also citing reduced regulatory risk and potential for tariff hikes, according to a note dated on Friday.
"We see room for potential tariff hikes in coming months as operators focus on reducing losses and pass the burden of higher spectrum on to consumers," Goldman wrote.