Try Quality Air Freight (
http://www.qasrs.co.za/) or Etosha Transport (
http://www.imperial.co.za/GD_ViewCompany.aspx?CompID=15 I think they only do bulk deliveries though). My company has used both of these companies for sending stuff to Namibia before. As far as I know the charges are lower than DHL (we use DHL as well, but they're expensive and in my experience they're pretty useless too).