****ing out of my electricity tokens

I buy my electricity from Citiq Prepaid in Pretoria. For the first couple of months things were fine. Then the wheels came off. Suddenly I had to pay the most expensive rate for ALL the units that I buy. They did not start at the cheap band they made me pay top rate, it did not matter if I bought 10 units or 100. I reported them to Nersa and it took almost two months before they admit what they were doing was wrong and set the price right. I think they do it on purpose and are most likely doing it to a lot of customers.