Pre legal Department

My account was handed over to the Pre legal Dept around October and I made arrangements to pay R500 via a debit order (Debi check)was activated every month until I finish up paying,on the 23rd of March was supposed to be my last month but to my surprised I am told that I still owe them,and I have been paying without failure, to my surprise i was served with a Surmon that time I was paying consistently...MBD books and Vodacom don't balance yet my account was debited