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>SMS is effectively piggybacking on the signals your phone sends out to find which towers are available, so were t-mobile being totally honest, they'd just cut

>SMS is effectively piggybacking on the signals your phone sends out to find which towers are available, so were t-mobile being totally honest, they'd just cut out the SMS charge period. It's still data and they still need to provision timeslots for it and transfer it. There is no free lunch. SMS goes over the signalling timeslot, in ISDN terms this is called the D-channel. D-channels cannot carry voice traffic. So provisioning more timeslots for D-channels, and consequently SMS, means that at a given tower and frequency you will have fewer timeslots for voice. So SMS has a cost. This analysis is not taking into account the cost of transferring SMS over the wired infrastructure as well.

asynchronous13 14y ago
In this case it is a free lunch. SMS was specifically designed to make use of an unused portion of communication between handset and tower. Thus, the limit of 1,120 bits (140 8-bit chars, or the now standard 160 7-bit chars). No extra time slots are needed to accomodate SMS, because it's bandwidth usage is dramatically lower than that of voice data. As you said, it's still data. If one has a plan that includes unlimited internet data, where is the justification to charge even more for SMS? But none of that really matters, because it's not the cost of the product that determines pricing. It's the delivered value that determines pricing.