PEC metering *****s from poor pensioner!

Life in a complex. We have prepaid electricity meters from PEC metering. I bought electricity for R500 on 6 July 2018. For R500 I only got 65,3 kwh units. They took R307 for a service charge. This never happened before. The service charge uses to be about R40 - R48. Even though I phoned them and they said they will look into it I have not receive an answer from them. As a pensioner this is ****************. They just ignore you.