Overcharged for a system error

I recently placed an order on the app,the flying fish was R145(48 pack) when you check out.I payed that amonut plus the delivery fee.Hours later R394,98 was deducted by Checkers sixty60 without my knowledge,I ended up not getting a refund,,saying it was a system error.Clearly blaming me as a customer in this case,Looks like the customer pays the price that they saw doesn't apply to them.I found it *****ulent of them to take money whithout my approval,saying in their Ts and Cs stipulates that,which means they ***** money from their customers!