My mobile phone provider has, without my knowledge or authorization, added a sim/phone number to my billing account. They have failed to inform me of this. I only found out when I realized my phone bill had exceeded the usual amount I pay for. I contacted my local phone provider, and the only information they could provide was that the sim belonged to a mobile phone model that does not exist/a bogus phone. I was then told to contact my mobile phone provider overseas customer service. After some time explaining that it was not me that gave permission and wanted to cancel this unknown sim/number, they agreed to look into cancelling this unknown sim. However, they are refusing to provide me exactly who it is, when and how this happened. I should mention that the only way for me to add another phone number to my billing account is to provide personal information to verify identification. Is this telephone slamming ('-an illegal telecommunications practice, in which a subscriber's telephone service is changed without their consent.')? Do I have the right to know who did this under Australian Consumer Law and how it happened?