Bad service

I have a contract for R199 data SIM. First for months they bill me more that the R199 when I query it they say it's usage but I have sufficient data so there is not usage. When I queried it another few times an agent just comes back and says that it was a subscription (that I never subscribed to by the way as this SIM is in a modem) and just says I am now unsubscribe. After this I get billed again for out of bundle I query it and they say it's usage yet there is still data on the sim. I paid them The R699 they billed me last month. This month it's R622 and they debit my account on the 18 August instead of the date we agreed on which is the last day of the month. I feel this is highly unfair as I am paying them yet they are exploiting me. How do you charge someone something they didn't use? Cause If it is out of bundle charges the some should not work yet they charge out of bundle and I have the data on my SIM that I subscribed to which I feel is day light *******.

Last month I contacted them and at least the agent made the usage to R1 which is good yet this month that usage of R1 has been used and I still have more than 70 gigs data. It feels as if they really robbing me.