If you want to limit what menu items a User has access to, do the following:
Go to Maintain>Security>Menu Item Permissions
Double click on the menu item you want (example: Transactions\Credit Cards\Authorize Credit Card)
Find the Role you want to affect (example: Customer Service)
Uncheck the "Execute" permission
Save
A User that has the Customer Service role will no longer be able to use that menu item.
Caution: If the user has other roles they may still have access to it.