Double Debits

I took personal loan with Nedbank last 2019 since then they have been debiting accordingly on my account up untill 16 january 2020 they started debiting twice and i kept on complaining as that kept on happening for 3 weeks i called and send complaints email but they only credited me for 2 debits am still waiting for 1 credit as it outstanding but still waiting and thus is fustrating because they can see that they debited extra on my profile but i have to run after them for credits or should i just change my banking details so that they can see how angry i am with their poor service!!!!!!!! its either they fix that or i stop paying period!!!!!!!!