I can't find anything about this on the Vodafone website but I've been told they're giving away VISA Gift Cards with any 24 month plan? It's online only this is what the email about it said:

$100 VISA Gift Card with any $60+ mobile phone plan (24mth)
$50 VISA Gift Card with any mobile phone plan up to $50 (24mth)

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4G available to customers with a 4G device, who have either an eligible 4G plan, or who have a current (4G) Data add-on added to any plan with Vodafone Alerts. The Vodafone 4G network has launched with coverage in selected major metro areas of Sydney and Perth, with some coverage in Melbourne, Adelaide, Brisbane, Gold Coast, Newcastle and Wollongong. Coverage will increase throughout the year, so check out the coverage checker for the latest network information.