In order to achieve your goal, you need to edit the template of the WizardPage element. There, you can reorder the borders named - PART_SideHeaderBorder and PART_HeaderBorder.
I would suggest you to work with our Implicit Styles as demonstrated in this help article
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal
and vote to affect the priority of the items