Hi Jan,
Labels are the last item which is drawn on a map in ArcMap. You can prevent label overplacing Annotations by using Feature Weight , see here ArcGIS Help (10.2, 10.2.1, and 10.2.2)
Annotations are features, therefor you can use that option.
Another way is described here: Esri Mapping Centre - Ask a Cartographer
hope that helps.
Kind regards,
Anna
*************************************
Technical Support Esri Germany