Airtel is the best network even your office shifted in basement area. It is costly more than other network but services are good. They provide good signal strength and data service also. My family is using Airtel SIM and we got always good network strength and stability. Their data plan are costly but overall company services are good. They are having good network coverage area also.Airtel network is number one network in India. Now Airtel is launching best internet 4G plan for their customer.