In Kenya calls to a competing network are so expensive that most people simply do not call across mobile phone networks. A chief executive of one of the mobile phone companies candidly admits that the high tariffs are a marketing strategy to keep subscribers. "It's a marketing decision. We want more people on our network. It started out as a cost issue but this is no longer the case." His counterpart at a competing network is even more blunt. "It's a tool to trap the customer inside the network, this is the rationale behind it."