Webafrica incorrect fibre billing

I have been struggling with Webafrica since end of March, in February I took their 100/50 fibre offer @799pm that is a good deal but the 40/10 @ R529 pm is sufficient for my family so I changed back down to the R529 package only for them to try and debit my account with R798 while I have already been downgraded to the 40/10 fibre. and they attempted to debit my account again for R798 on the 1st of May only difference now is that my fibre is off. Trying to explain this to the webafrica customer service is so simple anyone can see the fibre offerings that webafrica has but the lady tells me yes I must pay the R798 for the smaller fibre package currently billed @R529. All I want is for my service to be working again and the right amount of money to be debited from my account.