Incessant spamming, can't take NO for an answer.

I keep getting spam emails from Nedbank's Credit Card division. I have been called numerous times over the course of the past 2 to 3 months, and I keep telling them that I am not interested in a Credit Card. I have proceeded to block the number, but now I keep getting emails from them. Yesterday I received the fourth such an email. For the second time, this was from Bongeka Mbatha. I also received an email from this person on the 31st of October, where I responded that I am not intersted. Before that I also received an email from Ashik Sampat, 25th of October, who I also told that I am not interested. Before that, I was also contacted by Natashia Mazibuko on the 17th of October, and I also told her that I am not interested.

Now, I want to speak to someone who can actually do something about this incessant spamming. It's against the law (CPA and ECTA), and I demand an answer about this.