Refund on incorrect home loan debit not being paid.

Poor attention to detail and debiting my account for more than was due. When asked for my refund I am getting the run around. FnB debited more than what was owed as the final balance on my home loan despite me calling them to confirm the amount to be debited which I have proof of. Post this I have completed refund forms and now are being burdened with unnecessary admin and excuses. FNB service is shocking. How can we help you? Lol what a joke