Bad service

I have been struggling for the last 6 months with Andtin and Partners. My mother and late father was clients of them there debt was paid off 6 years ago now NedBank is sending my mother messages and calling that she owes them money. We have all the paperwork that says that both my parents owes nothing.I did contact Andtin and the are really bad in giving feedback a lady called Palesa just said we must ignore the phone calls but I mean who just ignores calls from people that says you owe them almost R42000,00. It has been a month now and still contact from the lady called Palesa. They are very bad in communicating with people