I am going to share my own experience. I am using airtel for the last 7 years.i tried almost all networks but I feel airtel is the best network. The reason behind this is even if you are in underground mall or between large buldings also you can find the single needle for to contact. They are providing 2g, 3g, 4g network with lower internet charges.
Another great advantages is their customer service. I can call them at any time with free of cost and my queries get resolved within a short period of time. I dont have any idea of porting to any other network because of its good service.About the call charges they recently launched new tariffs with free unlimited call to all numbers and data packs too with 99/149/199 rs respectively with data packs usage differs.with this new launch even all the low end people can also use data with low cost.Thank you for reading