over charged electricity bill

I have ap**** for prepaid meter in january then I was told to continue to pay my bill until the meter being installed of which idid so.I had a deposit with them of R3000.where by they said it will be refunded to me.Now they are saying they settled the balance I owe from jan to marchR 1981.11 which is impossible iam suppose to still have a credit balance with them.I spoke to Benry today he told me to visit their offices.