Unwanted marketing

This insurance group phone constantly wanting to market vehicle insurance. I never have given them any authorisation to call or use my personal information for whatever purpose. When asking them where they got my information from, it was said (I am not sure whether this is correct) "the National Consumer Database". I have tried to block them on my phone without success. I am of the opinion that they are not adhering to the Popi Act. I want them to remove my name from their database with immediate effect. When confronting the sales lady about this, the call was immediately terminated by her.