pathetic service

I have a contract for R199.00 data 10 gig day and 10 gig night after paying religiously for a year for the last 6 months they have been deducting R213.00 every month and i failed to understand why? i left it i went on maternity leave but the debit orders went off that was fine i gave birth lost my baby then because i came to work in the middle of the month my salary was short which meant 1 month arrears, immediately a consultant phones to tell me i need to pay? okay however all those R13.00 rand they have been deducting can make up 1 installment, i asked him can he tell me why i am paying more than what i signed for he was abrupt and wanted to drop the phone after i threatened that its bad customer service to drop the line on me he stayed on, I asked why i was paying more than required he told me about vat added tax???? excuse me? did anyone send a sms or email or phone call to say the amount will be going up? seriously you guys suck my contract expires this year sometime i will then finish it and cancel with no upgrade...