From time to time operators brings to market another offer for a predominantly non-voice communication. Several years ago, such tariff products is limited to providing significant discounts on SMS and were aimed at people with hearing and / or speech. Accordingly, the public sale were missing and a wide range of consumers were unknown. Today the mass market with pleasure "swallow" a rather big portion of such tariffs, but really interesting offers something not many. Maybe operators are no longer needed extra income? In contrast, revenue from VAS (value added services) are necessary and important as ever, but competent account the parameters of such non-voice tariff is non-trivial task. Error in either direction will be very unpleasant for the operator: in one case the rate will be known "stillborn" (ie useless) in the other - will provoke a reduction in income. Most likely, this is why operators are not particularly want to experiment, limited to careful tuning.