Incompitant to do their work

I had a credit card with FNB. This account was paid in full in November 2015. I lost my job a few months ago and informed your company about it. A few months later I was employed again but in a call centre. I specifically ask their office to call me before 08h00 or after 16h30 but no, they keep on harassing me during working hours with an demanding attitude. Lots of emails was sent to you regarding this, but no, I am still being called and sms just when you want to do that. The worst is that my account has been paid in full and FNB informed me the day when I closed my account that they will inform you about that. I am still getting calls from you with threatening messages just when you want to. I am not going to send you the proof again that this account has been paid, due to the fact that it is your responsibly to communicate with your client and bring your system up to date and to train your personnel to be professional. If this does not stop, I will bring an application against you to compel you and your client to stop harassing me