Non feature-linked labels with leader line

Hi everyone,

i am stuck on a labeling issue, hoping to be able to receive some useful hints here.

I have a point feature class which i need to label (non-feature-linked).
Using IAnnotateLayerPropertiesCollection and IBasicOverposterLayerProperties the labeling itself
is not a biggie. BUT: The leader line (set through IFormattedTextSymbol.Background) won't show in the map.

I suppose that you have to set the ILineCallout.AnchorPoint, but how can i achieve this using standard non-feature-linked labeling?
The desired AnchorPoint would be the labeled point feature itself.

Has anyone had to deal with an issue like this before?

Best Regards!