loan declined due to wrong details

i got a loan in june 2015 and was paying my loan every month - not in arrears, i want to apply for another loan and was told that my account was in arrears, which it isnt or wasnt, i can pull statements showing that every month it was paid, please i thought i will get better service at nedbank, but the fact that my record is bad due to arrears account which i paid every month is not good service at all, please sort it out