Accounts closed and paid up- Groenewald Lubbe harassing clients!

I have paid of my accounts in the first half of 2018. My accounts were handled by Linda Pillay. They left me alone and did not contact me, as everything has been paid. I have letters stating that my accounts were paid up. Last week i got a letter of demand. I called Linda and she said its a system error and they are sorting out. I got another mail, stating that they are going to trace my whereabouts due to no response. This needs to be sorted out ASAP!!!!!!!!