Paying for service I can't use

I have account with Telkom contract whereby I have been told every month that my debit did not go through due to insufficient fund even though i have funds in the account and they add additional R250 for failed debit to increase their revenue, I have met my contractual obligations every month making sure that after the "failed debit" I mannuly pay the agreed amount to them. I have tried to create a new debit order mandate with them unfortunately their incompetency has led me to same situation over and over. I have tried to get matter escalated and one of their consultants told me it can not be escalated and not I'm paying for the service that has been disconnected.