Hi,
Then, either:
- configure your "registration" menu item's access level so that only guests see it and configure another "control panel" menu item with an access level "registered" so that only registered users see it. That way, the users will use the menu item with the correct title to access the control panel
- turn off the display of the page heading in the settings of the "register" menu item
- edit the user / cpanel view via the menu Display>Views and set the title directly in a view override (I don't recommend this solution)