Australia is a large country but most of the population live in concentrated areas, mostly close to the coastline. In those populated areas, mobile telephones work with varying degrees of coverage, depending primarily on the particular network. Telstra is probably the most expensive of the networks but its 3G and 4G mobile phones work in many parts of the country where the other networks are non-functional. But even Telstra 3G and 4G phones do not work everywhere.