Over deduction by woolworths on personal loan

Took a loan of R1000 with Woolworths around 2016 march. They have been debiting my account since then till now. When ever I checked with Woolworths why are they debiting my account since the account was long fully paid no positive response. They kept on telling me that they will check and they will come back which they never do. I want Woolworths to refund me the money that they have over debited in my account since these was an agreement of 12 months