FNB loans

FNB has deducted the whole outstanding arrears from my account without consulting with me and without my authorization - I have tried to make payment arrangements with the loans department and No one picks up the calls you stay online for almost 20 min no answer. and the reason for the arrears is due to the same call center not picking up when i called in to change my banking details as i was not banking with FNB for 2 Months. Tried to call today to understand why the arrears are so high and equivalent to my installment and they Also deducted the monthly loan amount on top the arrears deducted and this happened on both my FNB loans. I would like this to be sorted out, as this is not according to the terms and conditions as signed in my contract.