Account settled but still debited

I have sent numerous emails and I’m not winning, I settled my account last month and you still debited R446,67 saying my account my in arrears due to a late and missed payment in January, I have send proof of payment that I did pay on time, they asked for statement as proof I sent that as well and now they telling me they can’t refund me as I owe them I need clarity of why my account was in arrears when they have been debiting