Indian regulator Trai has instructed Loop Mobile to inform its customers that it will cease services on November 29.
The struggling mobile operator's telecom license expires on that date, and Loop informed the regulator in March that it cannot afford to reacquire spectrum to keep its operations going.
Loop had also argued that it was entitled to an automatic 10-year license suspension, but regulators disagreed.
Trai has therefore told Loop to inform its customers of the closure, by mail SMS and email, by October 9, Press Trust of India said.
Bharti Airtel agreed in June to buy out Loop Mobile for a reported 7 billion rupees ($113.6 million). But regulators have yet to approve the deal and the spectrum would not be part of the deal.
Loop had already shut down operations everywhere but Mumbai after the fallout from the 2012 2G spectrum scandal.
When Airtel first announced it was negotiating on the terms of a buy Loop, it said the acquisition will give it another 3 million mobile customers and around 500 2G cell sites in the Mumbai area.