Of the major U.S. mobile operators, only Sprint so far offers a $99.99 all-you-can-eat plan covering full voice and data services. T-Mobile's competing plan adds unlimited text- and picture-messaging to calling. The report notes that two major Korean operators (SKT and KTF) offering video calls and global roaming have experienced degraded voice quality.
The increased usage of SMS text-messaging alone can flood the network and impair the quality of voice calls, said ABI. Furthermore, the cost of increasing capacity to meet demand, especially in carriers' backhaul operations, can erode any gains from flat-rate plans.
--Mark Walsh