Lack of response to double charge query

Have used Uber since it arrived in SA and had really positive experience until about a month ago, where was charged double for a routine ride/trip, which I had made on a number of occasions. Wrote at least 8 mails, send proof of payment on at least 3 occasions and til today not a response or refund. Wonderful technology however the poor or lack of much after service support makes it just another money making business with no customer focus.