Prefix 0457-138

Australia (officially the Commonwealth of Australia) is a sovereign country, located in Oceania between the Indian Ocean and the South Ocean. With an area of 7,692,024 square kilometres, is the largest country in Oceania and the sixth-largest country in the world. Australia's population was 25,918,400 people at 2021, equivalent to 0.33% of the world's total population. Australia is divided into six states and three internal territories: South Australia, New South Wales, Victoria, Western Australia, Queensland, and Tasmania. Australia's capital is Canberra, and most populous city is Sydney. A prosperous developed country, Australia is the world's 13th largesteconomy.

There are six main types of phone numbers in Australia. The most commonly used types are landline and mobile phone. Mobile numbers are numbers that are usually used in cell phones and linked to SIM cards. It can be used when moving to a new city or country. Mobile phone numbers have their own prefixes which are not geographical and are completely portable between mobile operators. In Australia, the length of the mobile phone number is ten digits and it starts with 04, followed by eight digits.

Telstra Corporation Limited is an Australian telecommunications and information services company headquartered in Melbourne, Victoria. Telstra is the largest telecommunications company in Australia, serving more than 18.8 million retail mobile phone customers, 3.8 million fixed-line bundle and standalone data subscribers, and about 960,000 retail standalone voice subscribers.