Bad Billing again.

These guys seem to bill me irregularly every month. Got a phone call previous month explaining the bad billing and promised from this month my amount would be as promised R569 but instead my bill is R794.61. They made excuses previous month also billed us twice that month did later reverse it. But even after trying to correct their mistake with a phone call they promised me this month it would be R569 but yet they messed it up with R794,61.