In addition to the base tariff plans, mobile operators in India also frequently sell STVs - Special Tariff Vouchers that provide below-the-line, tactical discounts. These are very localised (i.e., STVs found in
stores in one locality may not be sold in another part of the same city), and hence are usually hidden from media scrutiny.

While the STVs may be largely invisible from a top-down view, our survey showed that they could be quite significant in practice, with nearly half of our respondents using one or more STVs. Thus, one could get quite misled by just focussing on the base tariff plans in India, in our view.

OPerators are Raising STV packs
For example,
Vodafone in Mumbai had STV of Rs37 for 25p/min long distance calls which is now changed to Rs37 for
30p/min long distance calls