Incorrect money owed

My account was closed and paid up on the 03rd of July 2015, and for the last 3 months I have been getting statements saying I owe money, I have called the call centre about 7 times and all 7 consultants apologies and say they will correct this on their side and I wont be getting any more call or emails stating I owe money, but once again on a weekly bases im still getting SMS's saying I owe money and the collections department called saying I would be handed over. I cant believe that 7 consultants could not assist me.