SBS 2011 VL cals downgrade to SBS 2003 (OEM)

Hello,

Our Sales department has bought SBS 2011 Cal (6 of them) in the open license program for an costumer. But they are needed for an SBS 2003 server (OEM). They had 10, but they needed more.

But i cant find any keys or downgrade options on the volume license website for these cals.

Is it possible to get those licenses to work with SBS 2003?

Regards,

Hilbert