iPhones have a special way of handling calls outside of Voice Over Cloud control, here is the information to help understand that.
When you call someone with an iPhone and your displayed number is a fixed landline number from Australia, the iPhone checks the original number range allocation from the ACMA (Australian Communications and Media Authority). This number may have been reassigned to a smaller area than its original allocation, but Apple does not account for this. Additionally, it does not use the standard location database for registered numbers (IPND). To verify this, visit the ACMA website at https://thenumberingsystem.com.au and search for the number in the "Search for any number" section.
Apple is aware of this limitation, and has been informed they should be querying the current IPND location, please lodge a support case with Apple to help this corrected. https://support.apple.com/?cid=gn-ols-home-hp-tab