Unused bank account was not closed and now i owe R12500 after 12 years!!!!

In 2010 i opened an account with standard bank. I hardly ever used the account and lost the card. Yesterday i went to open a bank account on my name and they told me that i already have one and its arrears of R12500!!!!! I never once received any phone calls or emails or any correspondence from them. Ive had bank accounts with FNB and ABSA before over the last 10 years and after 3 months of not using those accounts they went dormant and closed. How can you charge me bank charges for 12 years when I'm clearly not using the account and then not even phone or notify me!?