I have been using airtel network for the last 5 years and I am completely satisfied with the nework coverage issue. As my phone is dual sim, so I always had some other sim card as well( which keeps changing every year or 2) , and being an architect I had to go to different sites in cities and states, so this was the network that I could trust in all my journeys. It is very rare for no network issue. Even my office was in basement and only airtel networks could reach there. It is bit coslier than other networks.