Useless call center and professional banker

I have a professional account and home loan account with Nedbank and since last 2 months Nedbank has been debitting my account twice for my home loan. If I phone there call center which obiviously takes lot of time to connect and they keep on transferring call to different deparments, it seems like they are not trained properly and useless, even my personal banker not communicating even after several emails, she has no courtesy, I don't know now whom to call and who will resolve my probelm as home loan is huge amount and twice debit every month is messing my monthly budget.