Paid off account and two years later admin fee out

I paid off my personal loan amount about 2 years ago, now I receive sms that there is a amount outstaning.I phoned them and they said it is admin fee for the loan that should have been closed 2 years ago.They now deducted R600 from my personal account.I want to know who gave them the right to deduct money from my account and they must pay back my money and cancel the fees.Someone did not do their job and now I must pay