I do not know why the other people rated airtel with 2 star, because in my opinion airtel is the best operator of india with all india availability. It also offers highest speed for 2g, 3g, 4g on mobile that makes it topper.
Airtel is the first out of them that started 4G in india.
& I am giving 1 less star only because of high cost for data plan but otherwise it is all good.
Choose it if you want an ultimate speed experience for your ultimate phone.