Got handed over just for skipping one payment on my personal loan

If made my payment for my personal loan and got a call from the legal apartment and they told me I have been handed over , I just missed one payment on Desember but made payments and still got handed over so tell me way? I just told the legal apartment hand me over but I already made my payment, just to inform you guys FNB is the badest bank ever and as soon as my loan is done I'm switching banks