Vodafone Australia has sacked several people after four million customer records were exposed in a privacy leak.
Vodafone employees allegedly sold private customer details and records with access to entire lists of calls and messages from individuals.
Company employees have been accused of selling the sensitive information to criminal gangs. The firm said it is reviewing its IT systems security, processes and training.
Vodafone Australia chief executive, Nigel Dews, said, "We've made swift progress. We've terminated the employment of a number of staff; we've undertaken a review of the security systems and processes, and we're implementing some of the initiatives straightaway."
Australian Privacy Commissioner Timothy Pilgrim has launched an investigation to determine whether the mobile firm breached the country's Privacy Act.