Bad service

In 2016 I went to close my Student account at the Standard bank Mowbray branch because I was no longer a student and unemployed at that time , they gave me a form to sign . 2021 November I went to Promenade branch to open a new account and to my surprise I was informed that the Student achiever is still active , it has accrued fees so I need to pay it first before opening the new account so I wasn't assisted .I told the lady I won't pay anything because I personally went to the branch to close this account, I never had an overdraft nor debit orders in that account they can check it .Due to Standard bank’s staff member who didn’t do their job I owe the bank of R5000( Service fees). On the 19th of May I sent an email to Claremont’s branch manager regarding this matter and she asked me if I still recall the staff member who assisted me in 2016 and further advised that I need to engage with their collections department. So was I supposed to go back to the branch to ensure that the account is closed ? This is is really frustrating and disappointing