This has been a pretty well know fact in the tech community. the mobile carriers have been overcharging everybody. almost 7 to 10 years back India had one of the most expensive mobile communication, but for the last 2 years it has been one of the cheapest areas, while this process of cost cutting was under way a rally was called for networks providing free SMSs always. The SMS text is sent in just the connectivity with the carrier tower connectivity signaling. No special protocol has to be envoked nor any special services to be provided. So the burden on the network is less than nominal.