Over billing without correcting

Reference number 1- ********** 7684 i went into the store at Westgate on 07/08/2017 to resolve the problem that my account has doubled in expense, they noticed they made a mistake and requested for reversal as data was loaded on my account that was not requested! i was told i would get a refund and it will not happen again . Phoned to confirm if everything is sorted, they confirmed it has been removed next 2 months data still being added and debited from my account with no refund still. Did not even use the extra data uploaded!! So upset with their service. I have phoned in 4 times every time with another explanation... Remove the data and refund my money how hard can that be!!