Over Debiting

Hi There, I owed Edgars about R8000 in interests even though I was still at school they kept on adding interests, I got a job and made arrangements to pay the money and they debited money from my account until they over debited by R287 , I enquired about it and I was told to send a copy of my bank statement , copy of my ID and a letter stating that I want the money paid back into my account , Now they are telling me that the amount belongs to an Agent that I didn't know about and nothing was communicated to me until I phoned again , please assist with this.