Utter incompetence from Daly credit corporation

I had an RSC account which was in areas, the account was handed over to daly credit corporation. We agreed on the settlement amount and the debit order went off on the 07/09/2020. My RCS account is now fully paid up. Whats funny is that I am still getting calls from agents of the above mentioned entity demanding payment. Utter incompetence if you ask me. No proof that my RCS Account has been settled, and im still being harrased by their agents demanding payment