Not all mobile phone owners are equal - at least not in the eyes of Nova 106.9, it would seem. The station's website lists the following competition rule:

4.4.3 SMS entry is available via compatible mobile phones which are connected to Telstra, Vodafone, Virgin Mobile, Optus mobile digital network and participating service providers. Entry is not currently available to those whose mobile phones are connected to 3, Orange mobile post-paid, Orange mobile pre-paid Optus MobilSat and Optus CDMA.