Standard bank student achiever account accumulated fees for dormant account

Student achiever account accumulated almost R11000 after 10 years of not being in use...even after closing the account at the branch,it shows no records...they tell you that you cannot transact with the student achiever account after 18 years of age but still charge you fees and interest 10 years after that...branch manager of Chatsworth states that i am liable to pay in full and close...there are no agreements or terms and conditions stating that fees have to be paid on a dormant student account...i was 17 when i opened the account because they came to my school...there were no documents that have been signed...i need the fees to be waivered.