Less Units

I bought 500 electricity this morning only to get 290 units. I mean how possible is that like W.T.F?????. When I call the customer centre they said that it is because I bought electricity a lot a months. I should buy once a month because the more I buy the less the units I will get. Does this Eskom also considering people like us the less fortunate who earn R1000 per week. IF I earn that obviously I will buy R100 electricity per week because I cant afford to buy 700 for the whole month. I think Eskom is only considering only the rich and whoever came up with idea is either selfish or was not using his brains.