DHL Consolidated let me down terribly.

I have been dealing with DHL consolidated for a number of years. On the 10th January, I received a parcel that was priced out of Spec. On closer investigation, DHL, without my consent changed the way the parcel must be expedited. They have confirmed it was an error on their side. I have been asking since then to receive the credit so I can cost my shipment correctly and 2 months later, I have not received anything. I have emailed the manager, Dirk Lombard who does not even reply. I guess this explains the lack of enthusiasm. DHL is a great freight company but if anything goes wrong, don't expect action