Unipin
Unipin prepaid electricity

I bought unipin electricity on the 21.10.2013 for R100 at the engine garage in mamelodi (Pretoria) but to my surprise when i entered it on the metre box it indicated 50 units. I normally buy R100 units from the place mentioned above and got 70 units and still the units i receive is a rip off. I think someone owe me an explaination cause i received 50% of what i paid for. I want this to be sorted out once and for all.
Voucher Pin number - 880608627
Serial number - 0001017639704
Date- 21/10/2013
Time - 11:10
Cashier - Dineo
Ref - 1668118333
Meter number - 07081912045
My name is Mandla