Concept Recoveries deducting money from my account even after i paid my debt in full.

My personal loan with African Bank was handed over to Concept Recoveries and i paid the loan in full by the 15 July 2020 and both Concept Recoveries and African Bank issued me with a paid up letter. But still Concept Recoveries continued on the 14 August to deduct money from my account of which i paid the account in full and the debit order was not supposed to happen, so i am now struggling to get a refund from them and they are saying they can not assist me in this matter. I must speak to African Bank, unfortunately African Bank has not received any money from them after my account was settled. How can i get assistance to get my money back that was deducted from my bank account.