Double charge refuse to refund

Sasol R101 filling station double charged me, I swiped the my card the first time and the cashier was adamant it did not go through although my Bank notified my the money was reserved , swiped the second time and that is when cashier agreed that it had gone through , I went through the effort of printing my statement to show the Manager 2 weeks ago and still no feedback or refund it seems like a tactic to rob customers can you someone please help as they make sure you do not get a receipt also.