Overcharged excessively

I have a 200GB a month data plan. I accidently went over my limit in November 2018. Cell C charged me almost R1500 for a few extra MB. I raised the issue was told to set a limit on my account to avoid it happening again by going to "manage account" and setting "out if bundle limit to 0"

I accepted my mistake, paid the excessive amount and went on. When my debit order went of for December 2018, it seemed I went over with 200MB and Cell C again debited an extra R1500 from my account. I followed there procedure and logged an issue. It has been 3 days without a response, this is unacceptable. Why have the limits if they don't mean anything and charging R1500 for 200MB, that seems insane. Even if it is "out of bundle"