2.5 years still awaiting my refund from GM Motors

I bought spares and service kit from GM Motors, of the purchased goods i returned spark plugs and the refund that was due to me was R600.00+ I have called and email several times. I have been sent from pillar to post. their account person who was suppose to process a refund had promised to call back. I follow up with him on many occasions via email and telephones to this day I still dont have my money.<br> If my money was in the back i could have earned interest. I think my next step will be to go the Ombudsman because still is so unprofessional, rude and inconsiderate.