I had it happen on my CNS > SYD / SYD > CNS Flexi - Upgrade to business class with 9,900 points and it's not an actual charge to any of your credit cards. The lovely lady at Velocity explained it's just how the system processes the upgrade. She explained it better though.
Join Australian Frequent Flyer (AFF) for free and unlock insider tips, exclusive deals, and global meetups with 65,000+ frequent flyers.AFF members can also access our Frequent Flyer Training courses, and upgrade to Fast-track your way to expert traveller status and unlock even more exclusive discounts!