Vodacome

I signed up for a contact with Vodacom beginning Aug 2021 with a monthly instalment of R499,00. The problem i have is vodacom debit my account every second month which results as a double debit. I have been querying this when i picked it up end of August and was told it has been sorted - obviously not. I am now again liable for a double payment which puts me out of pocket. Please sort this out as i will have no choice but to reverse the debit order to make a manual payment of what i am supposed to be paying. Please urgently assist and advise??