False billing

I was charged for something I DID NOT REQUEST FROM THE SERVICE PROVIDER (Telkom Mobile) . I CALLED TO GET A REFUND AND I WAS TOLD I WILL BE CREDIT WITH THE AMOUNT THEY OWE ME ON MY NEXT BILL, THIS WAS IN DEC 2015. IT IS NOW FEB 2016 AND I AM STILL RECEIVING INVOICES THAT HAVE NOT CREDITED THE PROMISED AMOUNT. I HAVE CALLED THEM ENOUGH TIMES. I AM UNSATISFIED CUSTOMER AND WILL NEVER USE YOUR SERVICES OR EVEN RECOMMEND ANYONE ELSE TO DO SO.