I have been using airtel for last five to seven years and I have seen them improving from 2G to 3G to 4G. But one thing that I have to say is that they do what they say. Their service is awesome, their customer care is very responsive and take care of every customer until they get satisfied. And the great thing about them is that they have offers for everybody. I have used their prepaid and postpaid both the services and they both are good. The one thing that I like the most about them is that they offfer great internet speeds even in 2G. They are very reliable and they have coverage to most of the parts of india.
If you are looking for a network which follows you everywhere then airtek is for you.