I found airtel mobile network just awesome. it gives coverages in every areas, even in very remorte areas like in far located villages. the call sound quality is very good, sounds during calling does not gets distorted by any means. also the airtel 3G is very fast internet connection. it is far more beter than aircel or vodafone. customer services is also very good.
Any complaints made in the customer care department, the remidy is done by them very quickly. the only problem is that it is very expensive.