acc paid 2013 butbeing harrased with final warning

I paid my woolworths account in full in 2013 closed my account I got a call 3 weeks that I owed them money and am overdue they said R100 plus I owe them I told whoever called me that I paid 2013 already and she said sorry and will call back ,next day i got sms from lawyer that I was handed over of which I called the lawyer and explaining so he told me that he will call back and will sort it out He never called the call centre woman never called and I am being harrassed every day with sms warnings for R100 that woolworths after 2 years states I am overdue of which I CLOSED AND PAID IN FULL IN 2013 I am trying to cooperate but fed up as nobodys helping I will get names and the lawyer firms name and his name when I at my expense must call them to solve this